JP2015132162A - Automatic penetration testing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic penetration testing machine capable of stably achieving load control by feedback while reducing an impact load when a penetration rod penetrates into the ground.SOLUTION: An automatic penetration testing machine 1 comprises a lifting stage 3, a chuck 5 that is provided on the lifting stage 3 and holds a penetration rod 4, a lifting motor 8 for performing the lifting and lowering operation of the lifting stage 3, a load cell for detecting a load applied to the tip of the penetration rod 4, and a control unit 10 which, after the lifting stage 3 at a lifted position has been lowered at a high speed by controlling the speed of the lifting motor 8 and immediately before the tip of the penetration rod 3 penetrates into the ground, issues a deceleration command to the lifting motor 8, and when the penetration rod 4 penetrates into the ground, switches the lifting motor 8 to load control and compensates the output torque of the lifting motor 8 as necessary while feeding back the value detected by the load cell, thereby applying a target test load.

Description

  The present invention relates to an automatic penetration testing machine used for determining the hardness of a ground as a preliminary survey of the ground.

  Conventionally, a Swedish sounding test method shown in Non-Patent Document 1 is known as an example of a test for determining hardness of a ground. In this test method, a penetrating rod having a screw point at the tip is vertically projected from the ground, and a weight is placed on the rear end of the penetrating rod in this state. Then, a load stage that performs so-called self-sinking with only a load by applying a load in six stages of 50N, 150N, 250N, 500N, 750N, and 1KN, and the rod under the load when the rod does not penetrate even at a maximum load of 1KN. Or it is comprised in two steps, the rotation step which rotates a screw point and performs what is called rotation penetration.

  Therefore, as an automatic penetration testing machine for automatically performing the above-described test, there is one disclosed in Patent Document 1. The automatic penetration testing machine includes a lifting platform that can be moved up and down along a standing column, a chuck that is provided on the lifting platform and supports a penetration rod, and a lifting drive unit that lifts and lowers the lifting platform. It is configured. The lifting platform is provided with a powder brake. The load applied to the lifting platform is adjusted by the braking force of the powder brake, and the test load is applied stepwise to the penetrating rod.

  Further, a strain gauge is affixed as a load detection means to the outer periphery of the chuck, and is configured to detect an actual load applied to the penetrating rod. While feeding back the detection signal, the braking force of the powder brake is adjusted to apply a test load to the penetrating rod.

Japanese Industrial Standard A1221 (Swedish Sounding Test Method)

JP-A-9-95931

  However, in the automatic penetration testing machine, if the braking force of the powder brake corresponding to the target test load is suddenly increased, an impact load is generated due to the influence of inertia. In this case, the load control is not stable in the feedback, and the test load cannot be properly applied.

The automatic penetration testing machine of the present invention was created in view of the above problems, and is provided with a penetration rod that penetrates into the ground, a lifting platform that can be moved up and down along an upright column, and the lifting platform. It is a holding means for holding the penetration rod, comprising a lifting drive means provided to the elevating operation of the elevation frame, and a load detecting means for detecting a load applied to the penetration rod de, at a predetermined height position In the stage of lowering a certain lifting platform until the tip of the penetrating rod comes into contact with the ground surface, speed control is performed to lower the lifting platform at a predetermined speed, and then in the step of penetrating the penetrating rod into the ground, the lifting platform by adjusting the load on an automatic penetrometer machine configured to perform a load control for loading a predetermined test load to penetration rod, switching from speed control to load control, the load detecting means Characterized in that it is performed when the detected value exceeds a preset threshold.

The penetrating rod has an engaging groove extending in a longitudinal direction on an outer periphery, and the holding means includes a steel ball that can be fitted into the engaging groove of the penetrating rod, and the steel ball is formed in the engaging groove. It is configured to hold the penetrating rod while being movable in the longitudinal direction, and the threshold value for switching from the speed control to the load control is that the steel ball moves inside the engagement groove. It is preferable to set a value higher than the frictional resistance value generated between the steel ball and the engagement groove .

According to the automatic penetration testing machine of the present invention, since the switching from the speed control to the load control is executed when the detection value by the load detection means exceeds a preset threshold value, the tip of the penetration rod When it reaches the ground surface, it can switch to load control and start the penetration test.

It is a perspective view of the automatic penetration testing machine of the present invention. It is a side view of the automatic penetration testing machine of the present invention. It is an AA line expanded sectional view of FIG. It is an expanded sectional view of the chuck | zipper part of the automatic penetration tester of this invention. It is a figure which shows the operation state of the automatic penetration testing machine of this invention. It is the figure which showed the drive control pattern of the raising / lowering motor of the automatic penetration testing machine of this invention in time series.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes an automatic penetration testing machine, which has a lifting platform 3 that can be moved up and down along a column 2. The elevator 3 includes a weight 3 a having a predetermined weight, a chuck motor 6, a penetrating rod 4 having a screw point 4 b at the tip of the rod 4 a, and an example of a holding means for the penetrating rod 4. A chuck 5 that can be rotated by the drive of the motor 6 and a lift motor 8 that is an example of a lift drive means for moving the lift 3 up and down are loaded.

  Further, as shown in FIG. 2, the lifting platform 3 has a sprocket 7 that rotates along a guide chain 2a that is arranged vertically along the support column 2, and the sprocket 7 rotates along the guide chain 2a. It is configured to move up and down. The penetrating rod 4 can be loaded with a load of 1 KN due to the lift 3 and the total weight loaded on the lift 3.

  As shown in FIG. 3, the sprocket 7 is connected so as to rotate integrally with the transmission shaft 12 via the planetary gear mechanism 11. A drive gear 13, an intermediate gear 14, and a transmission gear 15 are rotatably provided on the drive shaft 8 a capable of rotating in the forward / reverse direction of the lifting / lowering motor 8 as the lifting / lowering motor 8 is driven. The transmission shaft 12 is connected through the gear train and the one-way clutch 16. Specifically, the transmission gear 15 is formed in a cylindrical shape and has external teeth on its peripheral surface. The one-way clutch 16 is press-fitted into the transmission gear 15 so as to rotate integrally with the transmission gear 15 and is rotatably supported by the transmission shaft 12. By the action of the one-way clutch 16, the drive of the lifting motor 8 is transmitted to the sprocket 7 only in the direction in which the lifting platform 3 is lifted.

  A rotary encoder 17 is provided at the distal end of the transmission shaft 12 so that a pulse signal accompanying the rotation of the sprocket 7 can be output. And the control apparatus 10 mentioned later for details processes the pulse signal which the said rotary encoder 17 emits, and calculates | requires the penetration amount, penetration speed, etc. of the penetration rod 4. FIG.

  As shown in FIGS. 4 and 5, the chuck 5 is configured to be rotatable by connecting an endless chain 6 a to a chuck motor 6 provided on the elevator 3. The chuck 5 has a hollow cylinder 21 into which the penetrating rod 4 can be inserted. Three steel balls 20 that can be fitted in a concave engaging groove 4c formed in the side surface of the penetrating rod 4 are equally arranged on the upper surface of the cylinder 21 on the same surface. The steel ball 20 is supported by a sleeve 21b constantly biased upward by a spring 21a at a position that always protrudes into the inner hole of the cylinder 21, and engages with the engagement groove 4c of the penetrating rod 4. It is configured to hold this. When the sleeve 21b is pushed down against the bias of the spring 21a, the steel ball 20 becomes operable and the holding of the penetrating rod 4 can be released.

  A washer-type load cell 22, which is an example of load detection means, is inserted into the cylinder 21 of the chuck 5. A thrust load applied to the penetrating rod 4 is transmitted to the load cell 22 via a bearing that rotatably supports the cylinder 21. Due to this thrust load, the load cell 22 is distorted, and a strain gauge (not shown) attached to the load cell 22 is connected so as to detect the strain which is a minute change amount of the load cell 22 as an electric signal and transmit it to the control device 10. ing. Thereby, it is possible to detect the load applied to the penetrating rod 4.

  The said control apparatus 10 controls operation | movement of the automatic penetration testing machine 1, and is comprised so that the raising / lowering motor 8 may be drive-controlled according to a penetration condition. FIG. 6 shows the drive control pattern of the lifting motor 8 together with the detection value by the load cell 22 in time series.

  First, as shown in FIG. 6, in the stage from when the lifting platform 3 in the raised position is lowered until the tip of the penetrating rod 4 penetrates into the ground, the lifting motor 8 is driven by speed control. At the start of lowering, the penetration rod 4 is suspended from the chuck 5 as shown in FIG. Therefore, in this case, if the penetration resistance (direction in which the thrust load acts) is positive (+), the load cell 22 indicates the weight of the penetration rod 4 as a negative (-) value. In addition, when the weight of the penetration rod 4 is not detected by the load cell 22, it is comprised so that the fall of the raising / lowering stand 3 cannot be started. Thereby, although the penetration rod 4 is not mounted | worn, the situation which starts a test accidentally can be prevented.

  Then, from the start of the lowering of the lifting platform 3 until the tip of the penetrating rod 4 contacts the ground surface, a drive command is issued to the lifting motor 8 to lower the lifting platform 3 at a high speed.

  Subsequently, when the tip of the penetrating rod 4 comes into contact with the ground surface, the steel ball 20 located at the upper end of the engaging groove 4c rolls and moves toward the lower end of the engaging groove 4c as shown in FIG. . At the time of rolling, the detection value by the load cell 22 shows zero as shown in FIG. Thus, when the load cell 22 detects a load fluctuation from minus to zero, a deceleration command is issued to the lifting motor 8 and the lifting platform 3 is lowered at a low speed. With this configuration, when the tip of the penetrating rod 4 comes into contact with the ground surface, the impact applied to the penetrating rod 4 is reduced, and feedback control, which will be described in detail later, is stabilized.

  When the elevator 3 is lowered by the length of the engagement groove 4c, the steel ball 20 reaches the lower end of the engagement groove 4c and completes rolling. Even after the completion of rolling, if the elevating platform 3 continues to descend, penetration resistance acts gradually on the penetration rod 4 and the detection value by the load cell 22 rises. In this way, when the load cell 22 detects a load fluctuation from zero to plus, the lifting motor 8 is switched to load control and the output torque of the lifting motor 8 is adjusted so as to load the target test load (50 N). .

  By the way, there is a soft ground that cannot withstand the depression or the dead weight of the penetrating rod 4 on the ground surface, and the situation of the ground surface is different for each test point. In such a case, even if the tip of the penetration rod 4 reaches the ground surface, the penetration rod 4 cannot be resisted. For this reason, the rolling start timing of the steel ball 20 or the rolling completion timing differs for each test point.

  Therefore, according to the automatic penetration testing machine 1 of the present invention, as described above, based on the load fluctuation generated by the engagement state (rolling start or rolling completion) of the steel ball 20 and the engagement groove 4c, It is configured to issue a deceleration command to the lifting motor 8 or a switching command to load control. Therefore, it is possible to issue various commands to the lifting motor 8 at a desired position without any special design change regardless of the situation of the ground surface.

  In the load control stage, 50N, 150N, 250N, 500N, 750N, and 1KN test loads are applied in stages. Therefore, a load command is set in advance in the control device 10 so that the elevating motor 8 is driven with an output torque corresponding to these test loads.

  Further, in the automatic penetration testing machine 1 of the present invention, at the load control stage, the detection value by the load cell 22 is always fed back to compare the actual load with the target test load. If there is a difference between these as a result of comparison, a load command for increasing or decreasing the output torque of the lifting motor 8 is issued, and the target test load is actually loaded.

  Further, at the stage where the initial test load 50N is applied, when the detected value by the load cell 22 turns to a positive value, the output torque of the elevating motor 8 is not adjusted so that it immediately becomes the target test load, but by the load cell 22. After the detected value exceeds a preset threshold value, the load control stage is entered and a test load is applied.

  The purpose of setting the threshold value is that when the steel ball 20 rolls in the engagement groove 4c, the detection value by the load cell 22 may turn to positive before the rolling is completed due to the influence of friction. In particular, when soil is attached to the engagement groove 4c, the detected value temporarily rises when the steel ball 20 gets over this. In this case, before the rolling of the steel ball 20 is completed, it moves to load control contrary to the intention. If it shifts to load control before completion of rolling, it will descend rapidly between the remaining engaging grooves 4c in which the elevator 3 can roll. Therefore, the steel ball 20 contacts the lower end of the engaging groove 4c, and an impact load is generated. The impact load is too far from the target load. If feedback control is performed based on such a detected value, load control cannot be performed on stable feedback, and the test load cannot be applied properly.

  Therefore, the threshold value is set in advance to, for example, 10N with respect to the target load of 50N. And speed control is continued until the detection value by the load cell 22 exceeds the said threshold value, and if it exceeds a threshold value, the motor 8 for raising / lowering will be switched to load control (torque control). With this configuration, no impact load is generated, and stable feedback control is possible.

  Further, in the load control stage, a load command is issued so that the output torque of the elevating motor 8 is not suddenly increased to apply a test load, but the output torque is gradually increased to approach the target test load. By controlling the elevating motor 8 in this way, a sudden load increase (occurrence of impact load) due to the influence of inertia can be suppressed, and load control by feedback can be stably performed.

It should be noted that it is desirable to issue a load command so as to draw a sine curve locus at the stage where the load is gradually increased to approach the target test load. With this control, the fluctuation of the load is reduced, and the generation of the impact load described above is particularly reduced. Therefore, it is possible to realize load control with more and more stable feedback.

DESCRIPTION OF SYMBOLS 1 Automatic penetration test machine 2 Support | pillar 2a Guide chain 3 Lifting base 3a Weight 4 Penetrating rod 4a Rod 4b Screw point 4c Engaging groove 5 Chuck 6 Chuck motor 6a Endless chain 7 Sprocket 8 Lifting motor 8a Drive shaft 10 Controller 11 Planet Gear mechanism 12 Transmission shaft 13 Drive gear 14 Intermediate gear 15 Transmission gear 16 One-way clutch 20 Steel ball 21 Cylinder 21a Spring 21b Sleeve 22 Load cell

Claims (2)

A penetration rod having an engagement groove extending in the longitudinal direction on the outer periphery and a steel ball that can be fitted into the engagement groove of the penetration rod, and the steel ball is movable in the longitudinal direction inside the engagement groove The holding means for holding the penetrating rod and the lifting means that can be moved up and down along the support column are arranged, and a predetermined test load is applied to the penetrating rod by adjusting the load on the lifting base. In an automatic penetration testing machine configured to measure the amount of penetration of the penetration rod into the ground at the test load,
The steel ball of the holding means is positioned at the upper end inside the engaging groove until the tip of the penetrating rod comes into contact with the ground surface as the lifting platform at the predetermined height is lowered, and then the penetrating rod When the steel ball moves in the longitudinal direction in the engagement groove and reaches the lower end of the engagement groove as the elevator base descends, an initial test load is applied to the penetrating rod. An automatic penetration testing machine characterized by being configured as described above . The stage until the tip of the penetrating rod comes into contact with the ground as the elevator is lowered, and the tip of the penetrating rod comes into contact with the ground, and the steel ball of the holding means is engaged with the penetrating rod as the elevator is lowered. In the stage where the inside of the groove is moved from the upper end to the lower end, the speed control for lowering the lifting platform at a predetermined speed is executed,
  Subsequently, after the steel ball of the holding means has reached the lower end inside the engaging groove of the penetrating rod, load control for applying a predetermined test load to the penetrating rod is performed by adjusting the load on the lifting platform. The automatic penetration testing machine according to claim 1, wherein the automatic penetration testing machine is configured to be executed.

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