JP2549717B2 - Moving mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a moving mechanism, and more particularly to a moving mechanism used in industrial robots, NC machine tools and the like, and requiring a precise linear motion.

[Prior Art] The present applicant has previously proposed a moving mechanism capable of traveling with the guide bar held by the frictional force of the roller as a means capable of performing linear motion at high speed and with high accuracy. (Japanese Patent Application No. 62-113868-113870) According to this proposal, a movable base that is movable on a guide rail laid on a fixed base and a guide bar that is arranged on the fixed base in parallel with the guide rails. , Press against the guide bar,
A drive roller that is driven by a drive source provided on the moving table to move the moving table, and is provided in association with the moving table,
And a means for detecting the moving position of the moving table, wherein the movement of the moving table by the drive source is controlled via the means for detecting the moving position of the moving table.
With this configuration, it is possible to detect the moving position with high accuracy, and further, the moving table can be moved at high speed along the guide rail.

[Problems to be solved by the device]

However, in the moving mechanism as described above, the driving force is transmitted only by the frictional force between the guide bar and the driving roller on the moving table which is arranged so as to sandwich the guide bar. When it increased or when the environment between the guide bar and the drive roller changed (humidity, oil adhered), sufficient frictional force could not be obtained, and slippage might occur. If such slippage occurs, the guide bar and the drive roller will be significantly worn and the life of the device will be shortened.

Furthermore, if slippage occurs too much, the moving state becomes unstable and control becomes impossible. Further, it is difficult to predict the change in load and the change in environment in advance and calculate the necessary pressure contact force.

In view of the above-mentioned conventional problems, an object of the present invention is to provide a moving mechanism capable of reducing slippage of a driving roller, performing stable movement control, reducing wear, and prolonging the life of the device. Especially.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a movable base movable on a guide rail laid on a fixed base, a drive roller supported by the movable base and driven by a drive source on the movable base, and a fixed base. It is arranged parallel to the guide rail on the table,
A guide bar that keeps in contact with the drive roller, a pressure contact roller that is held by the moving base and is in pressure contact with the guide bar at a position facing the drive roller of the guide bar, a pressure contact force generation unit that applies a pressure contact force to the pressure contact roller, and a drive A rotation amount detecting means for detecting the rotation amount of the roller, a moving base detecting means for detecting the moving amount of the moving base, and a slip amount of the driving roller are detected based on the detection values of the rotation amount detecting means and the moving amount detecting means. A slip amount detecting means for comparing the absolute value of the slip amount per unit time by the slip amount detecting means with a predetermined reference value, and a judging means for judging an abnormal state when exceeding the predetermined reference value. It is a feature.

[Operation] According to the present invention, the rotation amount of the drive roller and the movement amount of the movable table are respectively detected by the detecting means, and the slip amount is detected by the slip amount detecting means based on the respective detected values. Then, this slip amount is compared with a predetermined reference value, and when it exceeds the predetermined reference value, the determination means determines that it is in an abnormal state.

Therefore, according to this determination, it is possible to increase the pressure contact force of the drive roller in the direction of decreasing the slip amount, or to stop the movement itself.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

 FIG. 9 shows an embodiment of the present invention.

A is a movable table movable on a guide rail laid on the fixed table, B is a drive roller supported by the movable table A and driven by a drive source on the movable table B, and C is a guide rail on the fixed table. A guide bar, which is arranged in parallel and keeps contact with the drive roller B, D is a press contact roller which is held by the moving base A and presses against the guide bar at a position facing the drive roller B of the guide bar C, and E is a press contact roller D. Pressing force generating means for applying a pressing force, F is a rotation amount detecting means for detecting the rotation amount of the drive roller B, G is a moving amount detecting means for detecting the moving amount of the moving base A, H is a rotation amount detecting means F and Moving amount detecting means G
A slip amount detecting means for detecting the slip amount of the drive roller B on the basis of the respective detected values, and J is a state in which the value detected by the slip amount detecting means H is compared with a predetermined reference value K, and when the predetermined reference value K is exceeded, an abnormal state is detected. Is a determining means for determining.

FIG. 1 shows an example in which the present invention is applied to an orthogonal robot. Here, 1 is a fixed base, 2 is a movable base capable of traveling on the fixed base 1, and 3 is a robot arm attached to the movable base 2. In this example, although not shown, a traveling member that is movable in the Y direction along the robot arm 3 is provided on the robot arm 3, and a robot hand that is vertically movable is provided on the traveling member.

4A and 4B are the first and the second arranged on the moving table 2.
The guide rails are two guide rails 4A and 4B arranged in parallel as shown in FIG. Further, 5 is a guide bar, the guide bar 5 is arranged in parallel with the guide rails 4A and 4B and in a hollow position on the fixed base 1, and both ends thereof are fixed by the bar fixing member 6 and the above-mentioned movement is performed. It is installed so as to pass through the space between the upper plate 2A and the lower plate 2B of the table 2. In addition, 2C, 2C is the upper plate 2
Spacers 2D, 2D provided between A and the lower plate 2B are sliding members slidably fitted in the guide rails 4A, 4B.

Numeral 7 is a servomotor mounted on the housing 2E mounted on the moving base 2 via a support base 8 as shown in FIG. 3, and the rotary shaft 7A of the motor 7 is driven by a drive roller shaft via a coupling 9. A drive roller 10 that is connected to the drive roller shaft 10A and is in contact with the side surface of the second guide bar 5 is attached to the tip of the drive roller shaft 10A. Reference numeral 7B is a first rotary encoder for detecting the amount of rotation of the rotary shaft 7A and thus the drive roller 10, and 11 is a bearing that axially supports the drive roller shaft 10A as shown in FIG.

Here, as shown in FIG. 3, the housing 2E has a hollow cylindrical shape, has an opening 2F cut along the guide bar 5 on the side surface thereof, and has an upper constituent plate 2A of the movable table 2.
It is equipped with a collar part 2G that is fixed to. Then, the drive roller shaft 10A is pivotally supported by fitting the bearings 11 above and below the housing 2E as shown in FIG. A flexible coupling is used for the coupling 9 so that the drive roller shaft 10A can be tilted.

With respect to the drive roller 10 which keeps contact with the guide bar 5 in this way, in this embodiment, as a means for pressing the drive roller 10 to the guide bar 5 on the side surface on the opposite side of the guide bar 5 as shown in FIG. A pressure roller holding member 12 is arranged. The pressure roller holding member 12 is mounted on the moving table 2 as shown in FIG.
The spring 13A in the spring storing member 13 fixed to the guide bar 5 is biased toward the guide bar 5 via the piston portion 12P kept liquid-tight, so that the drive roller 10 is brought into close contact with the guide bar 5. That is, a pair of pressure contact rollers formed of a metal material such as iron or steel provided on the pressure contact roller holding member 12
By keeping the guide bar 5 held between the 14 and the drive roller 10, the motor 7 can be driven and rotated to move the entire movable table 2 along the guide bar 5. In FIG. 4, 2F is a support frame that is erected from the movable table 2 side to hold the pressure roller holding member 12 slidably in the direction of the arrow.

Further, in FIG. 2, 34 is a sealing ring provided around the above-mentioned piston portion 12P, and this sealing ring 34 can keep the hydraulic chamber 13B of the spring storing member 13 liquid-tight from the spring storing chamber 13C. it can. Incidentally, 35 is a communication hole for communicating the spring storage chamber 13C with the atmosphere, and 36 is a control circuit 62 for the hydraulic chamber 13B.
Is a hydraulic pressure supply port for supplying a hydraulic pressure from a hydraulic pump 61 controlled by.

Therefore, by supplying pressure oil to the oil pressure chamber 13B through the oil pressure supply port 36, the piston portion 12P is moved leftward in FIG. 2 against the spring force of the spring 13A, and the pressure contact roller member 12 is moved.
The pressure contact force to the guide bar 5 is adjusted or released by.

Returning to FIG. 1 again, here, 21 is a second rotary encoder mounted on the moving base 2, and 22 is a pinion gear mounted on the encoder 21. However, the lever 22 is constructed so that backlash does not occur as shown in FIG.

That is, in FIG. 5, 22A and 22B are pinion gears provided in upper and lower two stages, and 23 is these pinion gears.
Rack gear that meshes with 22A and 22B, 24 is a pinion gear shaft, 2
5 is a coupling that connects the pinion gear shaft 24 and the shaft 21A of the second rotary encoder 21, and 26 is a bearing mounted on the lower base plate 2B of the moving base, which contains bearings 27A and 27B that support the pinion gear shaft 24. The case 28 is a cylindrical support member that supports the rotary encoder 21 provided on the bearing case 26.

FIG. 6 shows details of the pinion gear 22. Here, the upper pinion gear 22A is fixed to the gear shaft small diameter portion 24A,
The lower pinion gear 22B is loosely fitted in the gear shaft small diameter portion 24A. Also, the upper pinion gear 22A has a hooking pin 30A and
30B and through holes 31A and 31B are provided, and the lower pinion gear 22B is provided with hooking pins 32A and 32B which penetrate the through holes 31A and 31B in a loosely fitted state and project upward, respectively. A spring 33A is hooked between the pins 30A and 32A, and a spring 33B is hooked between the hooking pins 30B and 32B.

Therefore, when the pinion gear 22 meshes with the rack gear 23 provided on the fixed base 1, when the moving base 2 is moved along the guide rail 4 by the motor 7, the moving position or the moving amount is encoded. twenty one
Therefore, the movement of the moving table 2 can be accurately controlled via the encoder 12.

Further, when the movable table 2 is temporarily moved to an arbitrary position and is stopped there, the upper pinion gear 22A and the lower pinion gear 22B of the pinion gear 22 have springs 33A, 33B.
Since the urging force is maintained in the directions opposite to each other by the urging force, the backlash does not occur.

Returning to FIG. 1 again, 5A is a notch portion provided in the vicinity of the fixing member 6 of the guide bar 5, and the notch portion 5A as shown in this figure is provided on the side of the guide bar 5 where the drive roller 10 comes into contact. By providing the movable table 2 when the moving table 2 is moved to the end portion of the guide bar due to modulation of the drive circuit of the servo motor 7 or for some reason, the drive roller 10 falls into the cut portion 5A so that the other side of the guide bar 5 The pressure contact force acting from the surface can be eliminated, and the driving force of the movable table 2 can be eliminated and stopped.

Thus, when the robot arm 3 is moved in the direction of arrow x according to the control program of the robot (not shown), the servo motor 7 is driven according to the control program,
The movable table 2 can be moved in the same direction while the guide bar 5 is held between the driving roller 10 and the pressure roller holding member 12.

In the moving mechanism configured as described above, the reaction force F received by the drive roller 10 when the robot arm 3 is moved via the moving table 2 is determined by the conditions of the acceleration α of the robot arm 3 and its mass m. , Pressure roller 14
Must withstand its reaction force F and be kept in a state where no slip occurs between itself and the guide bar 5. That is, the friction coefficient between the guide bar 5 and the pressure roller 10 is μ
Then, It is necessary to set the pressure contact force P that satisfies the condition of the expression (1). Therefore, the pressure contact force P when the pressure oil is previously supplied to the hydraulic chamber 13B of the piston portion 12P and the spring 13A is slightly bent is It is set under the conditions as described above.

According to the present example, the drive bar 10 is moved by being driven by the motor 7 while the guide bar 5 is held between the drive roller 10 and the press contact roller 14 with the above-described press contact force P. The robot arm 3 can be freely moved to a desired position via the base 2, and the positioning by the movement is performed by the encoder 21.
Since it is obtained by the meshing state between the pinion gear device 22 and the rack gear 23 which are directly connected to each other without backlash, the robot arm 3 can be moved while maintaining highly accurate positioning.

Next, the moving state of the moving table 2 will be described with reference to FIG.
When the moving table 2 moves from the starting point X ₀ to the ending point X ₁ , the moving speed V of the moving table 2 gradually increases from “0” as shown in FIG. 7 (A). maximum speed
_Reach V _max (this section is called the acceleration zone). After that, the maximum speed V _max is maintained for a certain period of time (this section is called a constant speed area), and then the speed is gradually reduced and stopped (this section is called a deceleration area). The moving distance Ei of the moving table 2 is as shown in FIG. 7 (B). In this case, the driving force of the motor peaks in the acceleration and deceleration regions according to the well-known law of inertia. At this time, if a sufficient pressing force is applied between the drive roller 10 and the guide bar 5, both will not slip due to the frictional force. However, when the pressing force is insufficient, slippage occurs between the two.

The distance ei that the moving table 2 theoretically moves by the rotation of the driving roller 10 is as follows.

In the acceleration region, the theoretical moving distance ei becomes larger than the actual moving distance Ei of the moving table 2, and the difference becomes the slip amount (this case is referred to as positive slip). Even in the constant velocity region, the degree is small, but the tendency is similar. However, in the deceleration region, the opposite occurs and the actual travel distance Ei becomes larger than the theoretical travel distance ei (this case is referred to as negative slip). Since there are positive and negative slips in this way, comparing the theoretical travel distance ei at the end point X ₁ of travel with the actual travel distance Ei does not give an accurate evaluation of slip. .

Therefore, the movement time T of one cycle from the movement start point X ₀ to the end point X ₁ is time-divided, and the absolute value of the amount of slip between the drive roller 10 and the guide bar 5 per unit time is detected. I will do it. An example of the control procedure will be described with reference to the flowchart of FIG.

First, in step S1, the values of the counter number i of the counter, the accumulated slip amount Si, the actual movement amount Ei, and the theoretical movement amount ei are reset to 0 at the same time when the movement is started.

Next, in step S2, a timer for measuring the unit time Δt is started, and in step S3 the count number i is set to 1
I recommend.

Furthermore, in steps S4, S5 and steps S6, S7,
The second encoder 21 and the first encoder 7B respectively calculate the actual movement amount Ei and the theoretical movement amount ei of the moving base 2 at that time point, and take the difference from the previous value to calculate the unit time Δt, respectively. Calculate how much has changed.
Then, in step S8, the changes ΔEi and Δei per unit time are
The slip amount Δsi per unit time is calculated by taking the absolute value of the difference. This is shown in FIG. 7 (D). Further, in step S9, the current cumulative slip amount Si is added to the previous cumulative slip amount Si to calculate the current cumulative slip amount Si. The value is as shown in FIG. 7 (C).

Then, it is determined in step S10 whether or not this slip amount Si is larger than a reference value K ₁ that allows the movable table 2 to move normally. If it is larger than the reference value K ₁ , the process proceeds to step S11 to execute the abnormality relief described later.

If it is equal to or less than the reference value K ₁ , it is judged in step S12 whether or not the movement is completed.
The timer is reset at 4 and the process returns to step S2.

It should be noted that, in the above-described procedure, the determination as to whether it is abnormal or normal may be made based on the absolute value of the amount of slip ΔSi per unit time of spraying. However, in this case step
The reference value in S10 is determined as, for example, the reference value K ₂ of the slip amount per unit time.

Next, the execution of the abnormality relief in step S11 will be described. When the signal for executing the abnormality repair is output, the control circuit 62 sends a control signal to the hydraulic pump 61 to reduce the hydraulic pressure to be sent to the hydraulic chamber 13B and increase the urging force of the spring 13A of the piston portion 12P to increase the pressure contact roller 14 Therefore, the pressure contact force of the drive roller (10) and the pressure contact force of the drive roller (10) are increased to prevent slippage.

Alternatively, if slippage occurs beyond the capacity of the pressure contact force generated by the biasing force of the spring 13A, the hydraulic chamber 13B
The pressure of the spring 13A is shortened by increasing the hydraulic pressure to be supplied to and the movement of the moving table 2 is stopped by releasing the pressure contact force.

Since the above abnormality / normality judgment can be performed every unit time of about 5 msec according to the robot control program, the maximum moving speed of the moving table 2 is 1500 mm / sec.
It is possible to make an accurate judgment even by the degree.

In this embodiment, the actual amount of movement of the moving table 2 is detected by an encoder using a backlash-free rack and pinion. However, the present invention is not limited to this. The amount of movement may be detected using an optical sensor or the like.

Furthermore, it is also possible to use a value obtained by differentiating the cumulative value of the absolute value of the slip amount as the value indicating the degree of slip.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, the slip amount is detected from the actual movement amount and the theoretical movement amount of the moving table, and when the detected value exceeds the predetermined reference value, it is determined that the state is abnormal. As a result, the slip can be reduced or the moving table can be stopped accordingly, the movement of the apparatus can be controlled stably, and the life of the apparatus can be extended.

[Brief description of drawings]

1 is a perspective view showing an example of the structure of a moving mechanism of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, FIG. 3 is a perspective view of a bearing housing according to the present invention, and FIG. A perspective view schematically showing the drive system of FIG. 1 taken out, FIG. 5 is a sectional view of a moving position detecting mechanism according to the present invention, and FIG. 6 is an explanatory view of a pinion rack engaging portion shown in FIG. FIG. 7 is a graph for explaining the moving condition of the mobile table, FIG. 8 is a flowchart showing an example of a control procedure of an embodiment of the present invention, and FIG. 9 is a block diagram showing an embodiment of the present invention. 1 ... Fixed base, 2 ... Mobile base, 3 ... Robot arm, 4 ... Guide rail, 5 ... Guide bar, 7 ... Servo motor, 7A ... Drive shaft, 7B ... First rotary encoder , 10 ... drive roller, 12 ... pressure contact roller holding member, 12P ... piston part, 13A ... spring, 13B ... hydraulic chamber, 14 ... pressure contact roller, 21 ... second encoder, 22,22A, 22B: Pinion gear, 23: Rack gear, 36: Hydraulic pressure supply port.

Claims (2)

(57) [Claims] 1. A movable base which is movable on a guide rail laid on a fixed base, a drive roller which is supported by the movable base and is driven by a drive source on the movable base, and a fixed roller on the fixed base. Arranged in parallel with the guide rail,
A guide bar that keeps in contact with the drive roller, a pressure contact roller that is held by the movable table and presses against the guide bar at a position of the guide bar that faces the drive roller, and a pressure contact that applies a pressure contact force to the pressure contact roller. Force generating means, rotation amount detecting means for detecting the rotation amount of the drive roller, moving base detecting means for detecting the moving amount of the moving base, detection values of the rotation amount detecting means and the moving base detecting means, respectively. On the basis of the above, the slip amount detecting means for detecting the slip amount of the drive roller is compared with the absolute value of the slip amount per unit time by the slip amount detecting means and a predetermined reference value. A moving mechanism comprising: a determining unit that determines a state. 2. The judging means judges that an abnormal state is present when the cumulative value of the absolute values of the slip amount per unit time exceeds a reference value during one cycle. Moving mechanism.