Transport vehicle

Abstract

To provide a transport vehicle capable of suppressing the slip of wheels in the case of accelerating or decelerating a vehicle body.SOLUTION: A transport vehicle includes a vehicle body including first wheels and second wheels arranged at mutually different positions in a travel direction, a first driving device for driving the first wheels, a second driving device for driving the second wheels, and a control device for controlling the first driving device and the second driving device. The control device controls the first driving device and the second driving device so as to make a load increasing wheel torque ratio R being a ratio of torque to be transmitted to a load increasing wheel to the sum of first wheel torque and second wheel torque higher than during constant speed traveling of the wheel body with torque transmitted from the first driving device to the first wheels as the first wheel torque, with torque transmitted from the second driving device to the second wheels as the second wheel torque, and with wheels in which a vertically downward load increases by vehicle body acceleration or deceleration between the first wheels and the second wheels as load increasing wheels.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a guided vehicle that travels along a rail. [Background technology]

[0002] An example of such a carrier vehicle is disclosed in the following Patent Document 1. In the following description of the background art, the reference numerals in Patent Document 1 will be cited in parentheses.

[0003] The transport vehicle (3) of Patent Document 1 includes vehicle bodies (18, 19) having first wheels (25, 28) and second wheels (36, 37) disposed at different positions in the traveling direction and rolling on a traveling rail (4), drive devices (26, 29) that drive the first wheels (25, 28), and a control device (59) that controls the drive devices. The control device (59) generates a speed pattern (see FIG. 5 of Patent Document 1) based on a target position of the vehicle bodies (18, 19), and controls the drive devices (26, 29) in accordance with the speed pattern. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-282569 Summary of the Invention [Problem to be solved by the invention]

[0005] When the vehicle body (18, 19) accelerates or decelerates, the vertical downward load on one of the first wheels (25, 28) and the second wheels (36, 37) increases, while the vertical downward load on the other wheel decreases, which can result in increased wheel slippage and cause dust generation.

[0006] Therefore, it is desirable to realize a transport vehicle that can minimize wheel slippage when accelerating or decelerating the vehicle body. [Means for solving the problem]

[0007] In view of the above, the characteristic configuration of the transport vehicle is as follows: A transport vehicle that travels in a travel direction along a travel rail, a car body including a first wheel and a second wheel disposed at different positions in the traveling direction and rolling on the traveling rail; a first drive device that drives the first wheel; a second drive device that drives the second wheel; a control device that controls the first drive device and the second drive device, the torque transmitted from the first drive unit to the first wheel is defined as a first wheel torque, the torque transmitted from the second drive unit to the second wheel is defined as a second wheel torque, and one of the first wheel and the second wheel, on which a vertically downward load increases due to acceleration or deceleration of the vehicle body, is defined as a load-increasing wheel, The control device controls the first drive device and the second drive device so that, during acceleration and deceleration of the vehicle body, a load-increasing wheel torque ratio, which is a ratio of the torque transmitted to the load-increasing wheel to the sum of the first wheel torque and the second wheel torque, is made higher than when the vehicle body is traveling at a constant speed. death, the control device determines the first wheel torque based on at least one of a target position and a target speed of the vehicle body, and determines the second wheel torque based on multiplication of the determined first wheel torque by a set coefficient; the control device sets the setting coefficient to a specified reference value during the constant speed traveling, and during acceleration and deceleration of the vehicle body, if the first wheel is the load increasing wheel, sets the setting coefficient to a value smaller than the reference value, and if the second wheel is the load increasing wheel, sets the setting coefficient to a value larger than the reference value; When changing the first wheel torque, the control device causes a change period of the first wheel torque to coincide with a change period of the setting coefficient, When changing the first wheel torque, the control device smoothes the change in the first wheel torque using a moving average over a predetermined set period, and smoothes the change in the setting coefficient using a moving average over a period having the same length as the set period. It's at the point.

[0008] According to this characteristic configuration, the first wheel torque and the second wheel torque can be appropriately controlled in response to an increase or decrease in the vertically downward load acting on the first wheel and the second wheel while the vehicle is accelerating or decelerating. This makes it easier to minimize wheel slippage when accelerating or decelerating the vehicle. Furthermore, since the vehicle can be accelerated or decelerated with large speed changes, it is easier to improve the efficiency of transporting goods. Furthermore, according to this characteristic configuration, torque can be transmitted to the first wheel and the second wheel with an appropriate distribution both when the vehicle body is traveling at a constant speed and when the vehicle body is accelerating or decelerating. Furthermore, this characteristic configuration makes it easy to set the setting coefficient to an appropriate value at each point in time during which the acceleration of the vehicle body changes, thereby making it possible to transmit torque to the first wheel and the second wheel with an appropriate distribution while the vehicle body is accelerating or decelerating. Furthermore, this characteristic configuration can prevent sudden changes in the acceleration of the vehicle body and sudden changes in the setting coefficient, which makes it easier to stabilize the behavior of the vehicle body and reduces vibrations of the vehicle body in the traveling direction. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a transport vehicle according to an embodiment; [Figure 2] Control block diagram of a transport vehicle according to an embodiment [Figure 3] FIG. 10 is a schematic diagram illustrating the acceleration of the transport vehicle body according to the embodiment; [Figure 4] FIG. 10 is a schematic diagram illustrating a state in which the body of the transport vehicle according to the embodiment is decelerating; [Figure 5] 10 is a flowchart showing an example of a control process performed by a control device. [Figure 6] 1 is a time chart showing an example of a control process performed by the control device when accelerating a vehicle body from a constant speed traveling state. [Figure 7] 1 is a time chart showing an example of a control process performed by the control device when the vehicle body is decelerated from a constant speed traveling state. DETAILED DESCRIPTION OF THE INVENTION

[0010] A transport vehicle 100 according to an embodiment will be described below with reference to the drawings. As shown in Fig. 1, the transport vehicle 100 is configured to travel along a traveling rail 5. In this embodiment, the transport vehicle 100 is a ceiling-mounted transport vehicle that travels along the traveling rail 5 supported in a state of being suspended from the ceiling.

[0011] Here, the extension direction of the traveling rail 5 is referred to as the "front-rear direction X." In other words, the front-rear direction X is the direction along the traveling direction of the transport vehicle 100. The front side of the traveling direction of the transport vehicle 100 is referred to as the "front side X1," and the rear side of the traveling direction of the transport vehicle 100 is referred to as the "rear side X2." Furthermore, the direction perpendicular to the front-rear direction X when viewed vertically is referred to as the "width direction Y." Furthermore, the direction along the vertical direction is referred to as the "up-down direction Z." The upper side in the vertical direction is referred to as the "upper side Z1," and the lower side in the vertical direction is referred to as the "lower side Z2."

[0012] As shown in FIG. 1, the transport vehicle 100 includes a vehicle body 1. The vehicle body 1 includes a first wheel 11 and a second wheel 12. The first wheel 11 and the second wheel 12 are configured to roll on a traveling rail 5. The first wheel 11 and the second wheel 12 are arranged at different positions in the front-rear direction X. In this embodiment, the first wheel 11 is arranged on the rear side X2 of the second wheel 12. That is, in this embodiment, the first wheel 11 is a rear wheel, and the second wheel 12 is a front wheel.

[0013] In this embodiment, the pair of traveling rails 5 are arranged at an interval from each other in the width direction Y. Therefore, in this embodiment, the pair of first wheels 11 are arranged to roll on the pair of traveling rails 5, and the pair of second wheels 12 are arranged to roll on the pair of traveling rails 5.

[0014] In this embodiment, the vehicle body 1 further includes a holding unit 13 that holds an article A to be transported. In this embodiment, the holding unit 13 is supported while being disposed on the lower side Z2 of the traveling rail 5. The holding unit 13 is configured to support the article A in a suspended state.

[0015] As shown in FIG. 1, the transport vehicle 100 includes a first drive unit 2 and a second drive unit 3. The first drive unit 2 is configured to drive a first wheel 11. The second drive unit 3 is configured to drive a second wheel 12. Each of the first drive unit 2 and the second drive unit 3 includes, for example, a motor such as a servo motor and an axle driven by the motor. Each of the first drive unit 2 and the second drive unit 3 may also include a reducer that reduces the output rotation of the motor and transmits it to the wheel.

[0016] As shown in Fig. 2, the transport vehicle 100 is equipped with a control device 10. The control device 10 is configured to control the first drive device 2 and the second drive device 3. In this embodiment, the control device 10 is provided in the vehicle body 1. The control device 10 may be a combination of a first control device provided in the vehicle body 1 and a second control device (e.g., a higher-level controller) that is capable of communicating with the first control device and is provided separately from the vehicle body 1.

[0017] Here, a case where the vehicle body 1 traveling toward the front side X1 accelerates or decelerates will be described. As shown in Fig. 3, when the vehicle body 1 accelerates, that is, when the acceleration α of the vehicle body 1 is greater than zero, an inertial force toward the rear side X2 acts on the center of gravity G of the vehicle body 1. On the other hand, as shown in Fig. 4, when the vehicle body 1 decelerates, that is, when the acceleration α of the vehicle body 1 is less than zero, an inertial force toward the front side X1 acts on the center of gravity G of the vehicle body 1.

[0018] As shown in FIGS. 3 and 4, in this embodiment, the center of gravity G of the car body 1 including the article A held by the holding unit 13 is located on the side Z2 below the traveling rail 5. In this configuration, when the car body 1 traveling toward the front side X1 accelerates, as shown in FIG. 3, the vertically downward load P2 (load toward the downward side Z2) acting on the second wheel 12 increases, and the vertically downward load P1 acting on the first wheel 11 decreases. Furthermore, when the car body 1 traveling toward the front side X1 decelerates, as shown in FIG. 4, the vertically downward load P1 acting on the first wheel 11 increases, and the vertically downward load P2 acting on the second wheel 12 decreases. Note that in this embodiment, even when the article A is not held by the holding unit 13, the center of gravity G of the car body 1 is located on the side Z2 below the traveling rail 5.

[0019] In the following description, the wheel between the first wheel 11 and the second wheel 12 whose vertically downward load increases due to acceleration or deceleration of the vehicle body 1 is referred to as the "load-increasing wheel W." In this embodiment, while the vehicle body 1 is accelerating, the wheel between the first wheel 11 and the second wheel 12 that is located on the front side X1 (here, the second wheel 12) is the load-increasing wheel W. Meanwhile, while the vehicle body 1 is decelerating, the wheel between the first wheel 11 and the second wheel 12 that is located on the rear side X2 (here, the first wheel 11) is the load-increasing wheel W.

[0020] 5 is a flowchart showing an example of control processing by the control device 10. In the following description, the torque transmitted from the first driving device 2 to the first wheel 11 is referred to as "first wheel torque T1," and the torque transmitted from the second driving device 3 to the second wheel 12 is referred to as "second wheel torque T2."

[0021] As shown in FIG. 5, the control device 10 first determines a first wheel torque T1 based on at least one of a target position and a target speed of the vehicle body 1 (step #1).

[0022] Next, the control device 10 acquires the first wheel rotation speed N1, which is the rotation speed of the first wheel 11 (step #2). The first wheel rotation speed N1 can be detected by a rotation speed sensor provided on the vehicle body 1, for example.

[0023] Then, the control device 10 determines whether the first wheel rotation speed N1 is equal to or less than a predetermined threshold value TH (step #3). If the first wheel rotation speed N1 is equal to or less than the threshold value TH (step #3: Yes), the control device 10 sets the setting coefficient K to zero (step #4). The setting coefficient K is a coefficient used when determining the second wheel torque T2, as will be described later.

[0024] On the other hand, if the first wheel rotation speed N1 is greater than the threshold value TH (step #3: No), the control device 10 performs processing according to the traveling state of the vehicle body 1 (step #5). Specifically, if the control device 10 determines that the vehicle body 1 is traveling at a constant speed, it sets the setting coefficient K to a specified reference value s0 (step #6). Furthermore, if the control device 10 determines that the vehicle body 1 is accelerating or decelerating, it determines whether the first wheel 11 is a load-increasing wheel W (step #7). Whether the vehicle body 1 is traveling at a constant speed or accelerating or decelerating can be determined, for example, based on a change in the first wheel rotation speed N1.

[0025] When the control device 10 determines that the first wheel 11 is a load increasing wheel W (step #7: Yes), it sets the setting coefficient K to s1, which is a value smaller than the reference value s0 (step #8). On the other hand, when the control device 10 determines that the second wheel 12 is a load increasing wheel W (step #7: No), it sets the setting coefficient K to s2, which is a value larger than the reference value s0 (step #9). In this embodiment, since the first wheel 11 is a rear wheel and the second wheel 12 is a front wheel, when the first wheel 11 is a load increasing wheel W, the vehicle body 1 is decelerating (see FIG. 4), and when the second wheel 12 is a load increasing wheel W, the vehicle body 1 is accelerating (see FIG. 3).

[0026] The setting coefficient K can be calculated, for example, by the following equation (1). K = (P2 / P1) (RT1 / RT2) (1) where: P1: Vertical downward load acting on the first wheel 11 P2: Vertical downward load acting on the second wheel 12 RT1: Rated torque of first drive unit 2 RT2: Rated torque of second drive unit 3 (See Figures 3 and 4).

[0027] The load P2 can be calculated, for example, by the following formula (2). P2=M·(WB-WB2+H·α) / WB···(2) where: M: Total weight of one vehicle WB: Distance between the rotation axis of the first wheel 11 and the rotation axis of the second wheel 12 (wheel base) WB2: Horizontal distance between the rotation axis of the second wheel 12 and the center of gravity G of the body 1 H: Vertical distance between the top surface of the running rail 5 and the center of gravity G of the car body 1 α: Acceleration of vehicle 1 (See Figures 3 and 4).

[0028] The load P1 can be calculated, for example, by the following formula (3). P1 = M - P2 (3)

[0029] After setting the setting coefficient K, the control device 10 determines the second wheel torque T2 by multiplying the first wheel torque T1 by the setting coefficient K (step #10). In this embodiment, the control device 10 calculates the ratio of the second wheel torque T2 to the rated torque of the second drive device 3 by multiplying the ratio of the first wheel torque T1 to the rated torque of the first drive device 2 by the setting coefficient K.

[0030] As described above, when the vehicle body 1 is traveling at a constant speed, the setting coefficient K is set to s0, which is the specified reference value. On the other hand, when the vehicle body 1 is accelerating or decelerating, if the first wheel 11 is a load-increasing wheel W, the setting coefficient K is set to s1, which is a value smaller than s0, which is the reference value, and if the second wheel 12 is a load-increasing wheel W, the setting coefficient K is set to s2, which is a value larger than s0, which is the reference value.

[0031] Furthermore, as described above, the second wheel torque T2 is determined based on the multiplication of the first wheel torque T1 by the setting coefficient K. Therefore, when the vehicle body 1 is accelerating or decelerating and the first wheel 11 is the load-increasing wheel W, the second wheel torque T2 decreases compared to when the vehicle body 1 is traveling at a constant speed. On the other hand, when the vehicle body 1 is accelerating or decelerating and the second wheel 12 is the load-increasing wheel W, the second wheel torque T2 increases compared to when the vehicle body 1 is traveling at a constant speed. In other words, when the vehicle body 1 is accelerating or decelerating, the load-increasing wheel torque ratio R, which is the ratio of the torque transmitted to the load-increasing wheel W to the sum of the first wheel torque T1 and the second wheel torque T2, becomes higher compared to when the vehicle body 1 is traveling at a constant speed.

[0032] In this way, the control device 10 controls the first drive device 2 and the second drive device 3 so that, during acceleration and deceleration of the vehicle body 1, the load-increasing wheel torque ratio R, which is the ratio of the torque transmitted to the load-increasing wheel W to the sum of the first wheel torque T1 and the second wheel torque T2, is higher than when the vehicle body 1 is traveling at a constant speed.

[0033] In this embodiment, the control device 10 controls the first drive device 2 and the second drive device 3 so that, during acceleration and deceleration of the vehicle body 1, the load-increasing wheel torque ratio R is made higher than during constant speed traveling, within a range in which slippage between the load-increasing wheel W and the running rail 5 does not increase compared to during constant speed traveling.

[0034] In addition, in this embodiment, the control device 10 controls the first drive device 2 and the second drive device 3 so as to increase the load increasing wheel torque ratio R continuously or stepwise as the absolute value of the acceleration α of the vehicle body 1 increases.

[0035] Fig. 6 is a time chart showing an example of control processing by the control device 10 when the vehicle body 1 is accelerated from a constant speed traveling state. Fig. 7 is a time chart showing an example of control processing by the control device 10 when the vehicle body 1 is decelerated from a constant speed traveling state.

[0036] 6, the control device 10 maintains the acceleration α of the vehicle body 1 at zero until time t1, thereby keeping the traveling speed V of the vehicle body 1 constant, that is, causing the vehicle body 1 to travel at a constant speed. Therefore, until time t1, the vertically downward load P1 acting on the first wheel 11 and the vertically downward load P2 acting on the second wheel 12 are each maintained constant.

[0037] Furthermore, since the vehicle body 1 is traveling at a constant speed as described above, the control device 10 maintains the setting coefficient K at the reference value s0 during the period up to time t1. Accordingly, the load increase wheel torque ratio R is maintained constant during the period up to time t1.

[0038] The control device 10 increases the acceleration α from zero to the target acceleration during the period from time t1 to time t2. Therefore, during the period from time t1 to time t2, the vertically downward load P1 acting on the first wheel 11 decreases, and the vertically downward load P2 acting on the second wheel 12 increases.

[0039] At this time, in this example, the control device 10 smooths the change in acceleration α using a moving average over a predetermined set period. Specifically, in this example, a command (e.g., a position command or a speed command) that causes acceleration α to change instantaneously (in steps) from zero to the target acceleration at time t1 is used as a reference command, and the control device 10 controls the guided vehicle 10 based on a moving average command obtained by taking a moving average of the reference command over the set period. Therefore, in this example, the acceleration α increases linearly over the period from time t1 to time t2 (the time after the set period has elapsed since time t1).

[0040] The control device 10 also changes the setting coefficient K in accordance with changes in the acceleration α. ​​Here, the control device 10 increases the setting coefficient K in accordance with increases in the acceleration α. ​​In this example, the control device 10 smooths the change in the setting coefficient K using a moving average over a period of the same length as the setting period. The control device 10 also matches the change period of the acceleration α with the change period of the setting coefficient K. Specifically, a reference pattern is used for the change pattern of the setting coefficient K, in which the setting coefficient K instantaneously changes from a set value when the acceleration α is zero (e.g., a value calculated using the above formula (1); the same applies below) to a set value when the acceleration α is the target acceleration at time t1. In this example, the control device 10 sets the setting coefficient K according to a moving average pattern obtained by taking a moving average of the reference pattern over a period of the same length as the setting period. Therefore, in this example, the setting coefficient K increases linearly from time t1 to time t2. In this example, the value of the setting coefficient K after time t1 corresponds to s2, which is greater than the reference value s0.

[0041] As described above, in this embodiment, the first wheel torque T1 is determined based on at least one of the target position and the target speed of the vehicle body 1, and the second wheel torque T2 is determined based on multiplying the first wheel torque T1 by the setting coefficient K. Therefore, in this embodiment, the acceleration α of the vehicle body 1 has a value corresponding to the first wheel torque T1. In this way, when changing the first wheel torque T1, the control device 10 matches the change period of the first wheel torque T1 with the change period of the setting coefficient K. Furthermore, when changing the first wheel torque T1, the control device 10 smoothes the change in the first wheel torque T1 using a moving average over a predetermined set period, and smooths the change in the setting coefficient K using a moving average over a period having the same length as the set period.

[0042] During the period from time t1 to time t2, as the setting coefficient K increases in accordance with the increase in acceleration α, the loaded wheel torque ratio R also increases. In this example, during the period from time t1 to time t2, as the acceleration α increases linearly, the loaded wheel torque ratio R also increases linearly. In other words, as the absolute value of the acceleration α increases, the loaded wheel torque ratio R continuously increases.

[0043] The control device 10 maintains the acceleration α constant from time t2 onward. Therefore, from time t2 onward, the vertically downward load P1 acting on the first wheel 11 and the vertically downward load P2 acting on the second wheel 12 are each maintained constant.

[0044] Furthermore, the control device 10 maintains the setting coefficient K constant for a period after time t2, and accordingly, the load increase wheel torque ratio R is maintained constant for a period after time t2.

[0045] 7, the control device 10 keeps the acceleration α of the vehicle body 1 at zero until time t3, thereby keeping the traveling speed V of the vehicle body 1 constant, that is, causing the vehicle body 1 to travel at a constant speed. Therefore, until time t3, the vertically downward load P1 acting on the first wheel 11 and the vertically downward load P2 acting on the second wheel 12 are each kept constant.

[0046] Furthermore, since the vehicle body 1 is traveling at a constant speed as described above, the control device 10 maintains the setting coefficient K at the reference value s0 during the period up to time t3. Accordingly, the load increase wheel torque ratio R is maintained constant during the period up to time t3.

[0047] The control device 10 reduces the acceleration α from zero to the target acceleration during the period from time t3 to time t4. Therefore, during the period from time t3 to time t4, the vertically downward load P1 acting on the first wheel 11 increases, and the vertically downward load P2 acting on the second wheel 12 decreases.

[0048] At this time, in this example, the control device 10 smoothes the change in acceleration α using a moving average over a predetermined set period. Specifically, in this example, a command (e.g., a position command or a speed command) that causes acceleration α to change instantaneously (in steps) from zero to the target acceleration at time t3 is used as a reference command, and the control device 10 controls the guided vehicle 10 based on a moving average command obtained by taking a moving average of the reference command over the set period. Therefore, in this example, the acceleration α decreases linearly over the period from time t3 to time t4 (the time after time t3 that the set period has elapsed).

[0049] The control device 10 also changes the setting coefficient K in response to changes in the acceleration α. ​​Here, the control device 10 decreases the setting coefficient K in response to decreases in the acceleration α. ​​In this example, the control device 10 smooths the change in the setting coefficient K using a moving average over a period of the same length as the setting period. The control device 10 also matches the change period of the acceleration α with the change period of the setting coefficient K. Specifically, a reference pattern is used for the change pattern of the setting coefficient K, in which the setting coefficient K instantaneously changes from a set value when the acceleration α is zero to a set value when the acceleration α is the target acceleration at time t3. In this example, the control device 10 sets the setting coefficient K according to a moving average pattern obtained by taking a moving average of the reference pattern over a period of the same length as the setting period. Therefore, in this example, the setting coefficient K decreases linearly from time t3 to time t4. In this example, the value of the setting coefficient K after time t3 corresponds to s1, which is smaller than the reference value s0.

[0050] During the period from time t3 to time t4, the loaded wheel torque ratio R increases as the setting coefficient K decreases in accordance with the decrease in acceleration α. ​​In this example, during the period from time t3 to time t4, the loaded wheel torque ratio R increases linearly as the acceleration α decreases linearly. In other words, as the absolute value of the acceleration α increases, the loaded wheel torque ratio R continuously increases.

[0051] The control device 10 maintains the acceleration α constant during the period from time t4 onwards. Therefore, during the period from time t4 onwards, the vertically downward load P1 acting on the first wheel 11 and the vertically downward load P2 acting on the second wheel 12 are each maintained constant.

[0052] Furthermore, the control device 10 maintains the setting coefficient K constant for a period after time t4, and accordingly, the load increasing wheel torque ratio R is maintained constant for a period after time t4.

[0053] Other Embodiments (1) In the above embodiment, the load-increasing wheel torque ratio R is changed by changing the setting coefficient K in accordance with the running state of the vehicle body 1 and determining the second wheel torque T2 based on multiplying the first wheel torque T1 by the setting coefficient K, that is, the load-increasing wheel torque ratio R is changed by changing the second wheel torque T2 in accordance with the running state of the vehicle body 1 using the first wheel torque T1 as a reference. However, the present invention is not limited to such a configuration, and for example, the load-increasing wheel torque ratio R may be changed by increasing one of the first wheel torque T1 and the second wheel torque T2 and decreasing the other in accordance with the running state of the vehicle body 1.

[0054] (2) In the above embodiment, the load-increasing wheel torque ratio R is continuously increased as the absolute value of the acceleration α increases (see FIGS. 6 and 7). However, the present invention is not limited to such a configuration, and the load-increasing wheel torque ratio R may be increased in a stepwise manner as the absolute value of the acceleration α increases.

[0055] (3) In the above embodiment, the center of gravity G of the car body 1 is located on the Z2 lower side of the traveling rail 5, regardless of whether or not the holding unit 13 holds an article A. However, the present invention is not limited to such a configuration. For example, the center of gravity G of the car body 1 may be located on the Z1 higher side of the traveling rail 5 when the holding unit 13 is not holding an article A. Alternatively, the center of gravity G of the car body 1 may be located on the Z1 higher side of the traveling rail 5, regardless of whether or not the holding unit 13 holds an article A. Note that when the center of gravity G of the car body 1 is located on the Z1 higher side of the traveling rail 5, during acceleration of the car body 1, the first wheel 11 or the second wheel 12, whichever is located on the rear side X2, becomes the load-increasing wheel W, and during deceleration of the car body 1, the first wheel 11 or the second wheel 12, whichever is located on the front side X1 becomes the load-increasing wheel W.

[0056] (4) In the above embodiment, the setting coefficient K is calculated by the above formula (1). However, the present invention is not limited to such a configuration, and the setting coefficient K may be calculated by a formula other than the above formula (1) that is created based on experiments or the like.

[0057] (5) In the above embodiment, the change period of the first wheel torque T1 (acceleration α) and the change period of the setting coefficient K are matched. However, the present invention is not limited to such a configuration. For example, the change period of the first wheel torque T1 and the change period of the setting coefficient K may not completely match, but may only partially match.

[0058] (6) In the above embodiment, a configuration has been described in which the change in the first wheel torque T1 (acceleration α) is smoothed using a moving average over a predetermined set period, and the change in the setting coefficient K is smoothed using a moving average over a period of the same length as the set period. However, the present invention is not limited to such a configuration. For example, the value of the setting coefficient K during a change period of the first wheel torque T1 (acceleration α) may be set to a set value corresponding to the acceleration α at each point in time during the change period, rather than using a moving average based on a set value corresponding to the acceleration α at the start of the change period (e.g., a value calculated using the above formula (1); the same applies below) and a set value corresponding to the acceleration α at the end of the change period. Furthermore, at least one of the change in the first wheel torque T1 and the change in the setting coefficient K may not be smoothed.

[0059] (7) The configurations disclosed in the above-described embodiments can be applied in combination with configurations disclosed in other embodiments, as long as no contradictions arise. Regarding other configurations, the embodiments disclosed in this specification are merely examples in all respects. Therefore, various modifications can be made as appropriate within the scope of the present disclosure.

[0060] [Summary of the above embodiment] The following provides an overview of the above-described transport vehicle.

[0061] The transport vehicle is A transport vehicle that travels in a travel direction along a travel rail, a car body including a first wheel and a second wheel disposed at different positions in the traveling direction and rolling on the traveling rail; a first drive device that drives the first wheel; a second drive device that drives the second wheel; a control device that controls the first drive device and the second drive device, the torque transmitted from the first drive unit to the first wheel is defined as a first wheel torque, the torque transmitted from the second drive unit to the second wheel is defined as a second wheel torque, and one of the first wheel and the second wheel, on which a vertically downward load increases due to acceleration or deceleration of the vehicle body, is defined as a load-increasing wheel, The control device controls the first drive device and the second drive device so that, during acceleration and deceleration of the vehicle body, a load-increasing wheel torque ratio, which is the ratio of the torque transmitted to the load-increasing wheel to the sum of the first wheel torque and the second wheel torque, is higher than when the vehicle body is traveling at a constant speed.

[0062] This configuration allows the first wheel torque and the second wheel torque to be appropriately controlled in response to an increase or decrease in the vertically downward load acting on the first wheel and the second wheel while the vehicle is accelerating or decelerating. This makes it easier to minimize wheel slippage when accelerating or decelerating the vehicle. Furthermore, since the vehicle can be accelerated or decelerated with large speed changes, it is easier to improve the efficiency of transporting goods. As described above, this configuration makes it easier to minimize wheel slippage when accelerating or decelerating the vehicle body, thereby suppressing the generation of dust. Therefore, the above-described transport vehicle is suitable for use in clean rooms.

[0063] Here, it is preferable that the control device increases the load-increasing wheel torque ratio during acceleration and deceleration of the vehicle body compared to during constant speed traveling, within a range in which slippage between the load-increasing wheel and the running rail does not increase compared to during constant speed traveling.

[0064] According to this configuration, when the vehicle is accelerating or decelerating, a relatively large torque can be transmitted to the load-increasing wheels to allow the vehicle to travel within a range that minimizes wheel slippage.

[0065] Preferably, the control device increases the load increasing wheel torque ratio continuously or stepwise as the absolute value of the acceleration of the vehicle body increases.

[0066] As the absolute value of the acceleration of the vehicle body increases, the vertical downward load acting on the loaded wheel gradually increases. With the above configuration, the loaded wheel torque ratio is increased continuously or in stages in response to the increase in the vertical downward load acting on the loaded wheel. This allows the vehicle body to travel by efficiently transmitting a large torque to the loaded wheel during acceleration or deceleration of the vehicle body.

[0067] The vehicle body further includes a holding unit that holds an item to be transported, the center of gravity of the vehicle body including the article held in the holding portion is located below the traveling rail, During acceleration of the vehicle body, one of the first wheel and the second wheel that is located on the front side in the traveling direction is the load increasing wheel, Preferably, during deceleration of the vehicle body, one of the first wheel and the second wheel that is located rearward in the traveling direction is the load increasing wheel.

[0068] With this configuration, when the center of gravity of the car body including the item held in the holding part is located below the rail, the load-increasing wheel torque ratio can be appropriately increased during acceleration or deceleration of the car body, so that a relatively large torque can be transmitted to the load-increasing wheel to allow the car body to travel during acceleration or deceleration of the car body.

[0069] Further, the control device determines the first wheel torque based on at least one of a target position and a target speed of the vehicle body, and determines the second wheel torque based on multiplication of the determined first wheel torque by a set coefficient, The control device During the constant speed traveling, the setting coefficient is set to a specified reference value; During acceleration and deceleration of the vehicle body, if the first wheel is the load increasing wheel, the setting coefficient is preferably set to a value smaller than the reference value, and if the second wheel is the load increasing wheel, the setting coefficient is preferably set to a value larger than the reference value.

[0070] According to this configuration, torque can be transmitted to the first wheel and the second wheel with an appropriate distribution both when the vehicle body is traveling at a constant speed and when the vehicle body is accelerating or decelerating.

[0071] Preferably, the control device sets the setting coefficient to zero when the rotation speed of the first wheel is equal to or less than a predetermined threshold value.

[0072] According to this configuration, when the rotational speed of the first wheel is equal to or lower than the threshold value, the second wheel torque becomes zero, thereby making it possible to keep the energy consumption of the second drive device low while the vehicle body is stopped.

[0073] In addition, when the control device changes the first wheel torque, it is preferable that the control device matches a period during which the first wheel torque changes with a period during which the setting coefficient changes.

[0074] This configuration makes it easy to set the setting coefficient to an appropriate value at each point in time during which the acceleration of the vehicle body changes, thereby enabling torque to be transmitted to the first wheel and the second wheel with an appropriate distribution while the vehicle body is accelerating or decelerating.

[0075] In addition, when changing the first wheel torque, it is preferable that the control device smoothes the change in the first wheel torque using a moving average over a predetermined set period, and smooths the change in the setting coefficient using a moving average over a period of the same length as the set period.

[0076] This configuration can prevent sudden changes in the acceleration of the vehicle body and sudden changes in the set coefficient, making it easier to stabilize the behavior of the vehicle body and reducing vibrations in the direction of travel of the vehicle body. [Industrial Applicability]

[0077] The technology disclosed herein can be used in a transport vehicle that travels along a rail. [Explanation of symbols]

[0078] 100: Transport vehicle 1: Body 11:1st wheel 12: 2nd wheel 2: First drive unit 3: Second drive unit 5: Running rail 10: Control device W: Load increasing wheel T1: First wheel torque T2: Second wheel torque R: Load increase wheel torque ratio P1: Vertical downward load acting on the first wheel P2: Vertical downward load acting on the second wheel

Claims

1. A transport vehicle that travels in a travel direction along a travel rail, a car body including a first wheel and a second wheel disposed at different positions in the traveling direction and rolling on the traveling rail; a first drive device that drives the first wheel; a second drive device that drives the second wheel; a control device that controls the first drive device and the second drive device, the torque transmitted from the first drive unit to the first wheel is defined as a first wheel torque, the torque transmitted from the second drive unit to the second wheel is defined as a second wheel torque, and one of the first wheel and the second wheel, on which a vertically downward load increases due to acceleration or deceleration of the vehicle body, is defined as a load-increasing wheel, the control device controls the first drive device and the second drive device so that, during acceleration and deceleration of the vehicle body, a load-increasing wheel torque ratio, which is a ratio of the torque transmitted to the load-increasing wheel to the sum of the first wheel torque and the second wheel torque, is made higher than when the vehicle body is traveling at a constant speed; the control device determines the first wheel torque based on at least one of a target position and a target speed of the vehicle body, and determines the second wheel torque based on multiplication of the determined first wheel torque by a set coefficient; the control device sets the setting coefficient to a specified reference value during the constant speed traveling, and during acceleration and deceleration of the vehicle body, if the first wheel is the load increasing wheel, sets the setting coefficient to a value smaller than the reference value, and if the second wheel is the load increasing wheel, sets the setting coefficient to a value larger than the reference value; When changing the first wheel torque, the control device causes a change period of the first wheel torque to coincide with a change period of the setting coefficient, When changing the first wheel torque, the control device smoothes the change in the first wheel torque using a moving average over a predetermined set period, and smooths the change in the setting coefficient using a moving average over a period of the same length as the set period.

2. 2. The transport vehicle according to claim 1, wherein the control device increases the load-increasing wheel torque ratio during acceleration and deceleration of the vehicle body, compared to during constant speed travel, within a range in which slippage between the load-increasing wheel and the traveling rail does not increase compared to during constant speed travel.

3. The transport vehicle according to claim 1 , wherein the control device increases the load-increasing wheel torque ratio continuously or stepwise as the absolute value of the acceleration of the vehicle body increases.

4. The vehicle body further includes a holding unit that holds an item to be transported, the center of gravity of the vehicle body including the article held in the holding portion is located below the traveling rail, During acceleration of the vehicle body, one of the first wheel and the second wheel that is located on the front side in the traveling direction is the load increasing wheel, The transport vehicle according to claim 1 , wherein, during deceleration of the vehicle body, one of the first wheel and the second wheel that is located rearward in the traveling direction is the load increasing wheel.

5. The transport vehicle according to claim 1 , wherein the control device sets the setting coefficient to zero when the rotation speed of the first wheel is equal to or less than a predetermined threshold value.

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