A method and structure for counteracting friction in a Coriolis scale

Abstract

This invention relates to the field of powdered material flow metering devices. The technical solution is: a method for counteracting friction in a Coriolis scale, applied to a side-mounted Coriolis scale, characterized by: the method comprising: setting the drive shaft support bearing connected to the drive shaft as an internal bearing of the motor; and setting the motor support connecting to the force sensor and the machine base as a relatively rotatable floating structure via bearings, so that the friction force of the drive shaft support bearing becomes an internal force, thereby eliminating the interference of the drive shaft support bearing friction force on the force sensor; setting the outer ring of the passive shaft support bearing connected to the driven shaft and the machine base as a relatively rotatable floating structure via bearings; and setting a friction force counteracting mechanism between the motor support and the outer ring of the passive shaft support bearing. This method and structure should be able to eliminate bearing friction in the drive and passive shaft systems of the Coriolis scale, improving the metering accuracy and operational stability of the Coriolis scale.

Description

Technical Field

[0001] This invention relates to the field of powdered material flow metering devices, specifically a method and structure for counteracting friction in a Coriolis scale. Background Technology

[0002] A Coriolis scale (also called a Coriolis force scale) is a quantitative feeder for powdered materials that automatically weighs and controls the instantaneous flow rate. Coriolis scales are widely used in industries such as building materials, cement, power, chemicals, and food processing for dynamic weighing and quantitative feeding of various powdered materials during production. Its working principle is as follows: The core component of a Coriolis scale is a measuring disc. The material being measured falls onto the measuring disc and is thrown off by the rotating disc. The material exerts a force on the blades of the measuring disc; this force is the Coriolis force. This force generates a reverse torque on the measuring disc, which is proportional to the mass of the material. Measuring the magnitude of this force yields the material flow rate. In a Coriolis scale, what is measured is the torque of the driving shaft of the measuring disc. Since the radius of the measuring disc is fixed, measuring the torque yields the Coriolis force, and thus indirectly, the instantaneous flow rate of the material.

[0003] Depending on the installation position of the drive motor, Coriolis scales typically come in two forms: one where the drive motor is positioned above the scale body, directly driving the main shaft of the measuring pan to rotate; and another where the drive motor is positioned on the side of the scale body, driving the main shaft of the measuring pan to rotate via a transmission mechanism. Because materials in a side-mounted Coriolis scale can fall directly to the center of the measuring pan, avoiding the problem of low measurement accuracy caused by uneven loading of the measuring pan, and also facilitating heat dissipation and maintenance, the side-mounted type is currently the most common type of Coriolis scale.

[0004] For example, Chinese patent CN205228547U discloses a side-mounted Coriolis scale employing a flexible force transmission mechanism. This Coriolis scale includes a metering chamber with an inlet and an outlet, a main shaft mounted within the metering chamber, and a drive device for rotating the main shaft. A measuring disc is connected to the main shaft, with the inlet located directly above the measuring disc. The drive device is located outside the metering chamber and is connected to the main shaft via a synchronous belt drive. The drive device uses a motor, and a motor mounting bracket is provided outside the metering chamber. The motor mounting bracket has a motor mounting seat, which includes a fixed portion fixed to the motor mounting bracket and a rotating portion rotatably engaged with the fixed portion. Both the rotating and fixed portions have shaft holes through which the motor's output shaft passes. The motor base is fixed to the rotating portion, and a sensor detection device is fixed to the motor mounting bracket. The sensor detection device's measuring contacts abut against the motor base to lock the motor base and detect the torque on the motor's output shaft.

[0005] The working principle of the Coriolis scale in the aforementioned patent is as follows: When the motor is started, the motor base remains stationary due to the locking effect of the sensor detection device. The output shaft drives the main shaft to rotate and drives the measuring disk to rotate. The material falls into the middle of the measuring disk from the feed port. Under the action of centrifugal force, the material hits the blades of the measuring disk. The measuring disk is subjected to the force of the material. Assuming the rotation direction of the main shaft and the output shaft is positive, the main shaft will be subjected to a reverse torque. When the main shaft is subjected to torque, the output shaft will also be subjected to a reverse torque through the connection of the synchronous belt. In this way, the motor base will generate a forward rotation tendency. The measuring contact of the sensor detection device is subjected to the force of the motor base and detects the resistance torque of the main shaft when the material hits the blade, thereby detecting the flow rate of the material.

[0006] However, in the Coriolis scale described in the aforementioned patent, both the motor's output shaft and the main shaft of the measuring disc are directly supported on the base via bearings. When the Coriolis scale operates, friction is generated in the bearings. This friction is detected by the sensor and treated as Coriolis force. This friction is a variable affecting the measurement accuracy of the Coriolis scale, leading to reduced zero-point stability and impacting operational stability. Therefore, the calibration coefficient needs to be adjusted multiple times during use. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and structure for counteracting friction in a Coriolis scale. This method and structure should be able to eliminate bearing friction in the active and passive shaft systems of the Coriolis scale, thereby improving the measurement accuracy and operational stability of the Coriolis scale.

[0008] The technical solution provided by this invention is:

[0009] A method for counteracting friction in a Coriolis scale, applied to a side-mounted Coriolis scale, characterized in that the method includes:

[0010] By setting the drive shaft support bearing connected to the drive shaft as an internal bearing of the motor, and setting the motor support and the base connected to the force sensor as a floating structure that can rotate relative to each other through the bearing, the friction force of the drive shaft support bearing is transformed into an internal force, thereby eliminating the interference of the drive shaft support bearing friction force on the force sensor.

[0011] The outer ring of the passive shaft support bearing connected to the passive shaft is set to a floating structure that can rotate relative to the base via the bearing. A friction cancellation mechanism is set between the motor support and the outer ring of the passive shaft support bearing. The friction force of the passive shaft support bearing is converted into a tensile force applied to the motor support through the friction cancellation mechanism, thereby eliminating the interference of the friction force of the passive shaft support bearing on the force sensor.

[0012] The motor support and the outer ring of the passive support bearing are flexibly connected by the friction-counting mechanism, which allows the motor support and the outer ring of the passive support bearing to move slightly around their own axes.

[0013] A structure for counteracting friction in a Coriolis scale includes a base, a drive shaft, a motor for driving the drive shaft to rotate, a motor support fixedly connected to the motor stator, a driven shaft parallel to the drive shaft and spaced apart, a driven shaft support bearing with its inner ring fixedly connected to the driven shaft, a measuring disc fixedly connected to the driven shaft, and a transmission mechanism connecting the drive shaft and the driven shaft; characterized in that:

[0014] A force sensor is installed on the motor support; a drive shaft support bearing is provided between the drive shaft and the motor support; the inner ring of the drive shaft support bearing is fixedly connected to the drive shaft, and the outer ring of the drive shaft support bearing is fixedly connected to the motor support; the motor support and the machine base are configured as a floating structure that can rotate relative to each other through bearings; the outer ring of the passive shaft support bearing and the machine base are configured as a floating structure that can rotate relative to each other through bearings; a friction cancellation mechanism is provided between the motor support and the outer ring of the passive shaft support bearing.

[0015] A support bearing is provided between the motor support and the machine base; the inner ring of the support bearing is fixedly connected to the motor support, and the outer ring of the support bearing is fixedly connected to the machine base.

[0016] The outer ring of the passive shaft support bearing is fixedly sleeved with a protective shaft; a protective shaft support bearing is provided between the protective shaft and the machine base; the inner ring of the protective shaft support bearing is fixedly connected to the protective shaft, and the outer ring of the protective shaft support bearing is fixedly connected to the machine base.

[0017] The motor support and the sheath shaft are flexibly connected by a steel wire rope; the steel wire rope and the sheath shaft together form the friction cancellation mechanism.

[0018] The transmission mechanism adopts belt drive or gear drive.

[0019] The drive shaft support bearing, the support bearing, the passive shaft support bearing, and the sheath shaft support bearing are all ball bearings.

[0020] The active shaft support bearing, the support bearing, the passive shaft support bearing, and the sheath shaft support bearing are respectively arranged in two sets, one above the other, to improve the working stability of the Coriolis scale.

[0021] The motor support has a lower end cover fixed to the bottom and sleeved on the outer circumference of the drive shaft; the lower end of the sheath shaft has a lower end cover fixed to the bottom and sleeved on the outer circumference of the driven shaft; the two ends of the wire rope are respectively fixedly connected to the lower end cover of the support and the lower end cover of the sheath shaft.

[0022] The beneficial effects of this invention are:

[0023] (1) In the active shaft system of the present invention, an active shaft support bearing is provided between the active shaft and the motor support, and a support bearing is provided between the motor support and the machine base, so that the active shaft support bearing becomes the internal bearing of the motor, and the friction of the active shaft support bearing becomes the internal force, which will not be transmitted to the force sensor, thus eliminating the interference of the friction of the active shaft support bearing on the force sensor.

[0024] (2) In the passive shaft system of the present invention, a passive shaft support bearing is provided between the passive shaft and the sheath shaft, a sheath shaft support bearing is provided between the sheath shaft and the base, and a friction force cancellation mechanism is provided between the motor support and the sheath shaft. When analyzing the active shaft system as a whole, due to the tension of the wire rope, the force of the motor support detected by the force sensor will be reduced. The reduced force of the motor support is the friction force of the passive shaft support bearing. This is equivalent to the friction force of the passive shaft support bearing not being transmitted to the force sensor under the action of the friction force cancellation mechanism, thus eliminating the interference of the friction force of the passive shaft support bearing on the force sensor.

[0025] (3) The motor support and the sheath shaft of the present invention are flexibly connected by a steel wire rope, so that the sheath shaft will rotate at a small angle around its own axis due to inertia under the friction of the passive shaft support bearing, so as to counteract the tension of the steel wire rope and ensure the rationality of the structure.

[0026] (4) This invention greatly improves the measurement accuracy and operational stability of Coriolis scales, solves the industry problem of inaccurate measurement accuracy and the need for multiple adjustments of calibration coefficients, and is suitable for widespread application. Attached Figure Description

[0027] Figure 1 This is a front view of the structure of the present invention.

[0028] Figure 2 This is a top view of the structure of the present invention.

[0029] Icon labels:

[0030] 1. Drive shaft system; 1-1. Motor; 1-2. Drive shaft; 1-3. Drive shaft support bearing; 1-4. Motor support; 1-5. Support bearing; 1-6. Lower end cover of support; 1-7. Force sensor; 1-8. Rigid rod;

[0031] 2. Passive shaft system; 2-1. Measuring disc; 2-2. Passive shaft; 2-3. Passive shaft support bearing; 2-4. Sheath shaft; 2-5. Sheath shaft support bearing; 2-6. Lower end cover of sheath shaft;

[0032] 3. Transmission mechanism; 4. Wire rope; 5. Machine base. Detailed Implementation

[0033] The following description, in conjunction with the embodiments shown in the accompanying drawings, provides further details.

[0034] In the operation of the existing side-mounted Coriolis scale, assuming that the rotation direction of the drive shaft 1-2 and the driven shaft 2-2 is positive, after the material falls onto the measuring plate, the material is thrown out from the edge of the measuring plate 1-1, which will generate a Coriolis force on the measuring plate blades, causing the driven shaft to be subjected to a reverse torque (this reverse torque is proportional to the material flow rate). This reverse torque can be transmitted to the drive shaft through the transmission mechanism 3. Since the motor support 1-4 and the base 5 are connected by the support bearing 1-5, the motor support will have a forward rotation tendency. The force sensor 1-7 detects the force F1 of the motor support, and can obtain the reverse torque on the driven shaft, thereby detecting the material flow rate.

[0035] Since the drive shaft is mounted on the base via drive shaft support bearing 1-3 and the driven shaft is mounted on the base via driven shaft support bearing 2-3, the drive shaft system (including motor 1-1, motor support 1-4, drive shaft support bearing 1-3 and support bearing 1-5), the driven shaft system (including driven shaft 2-2, measuring disk 2-1 and driven shaft support bearing 2-3) and the transmission mechanism are analyzed as a whole. According to the force balance, the torque actually measured by the force sensor 1-7 includes: the measuring disk working torque M0 generated by the Coriolis force of the measuring disk, the driven shaft system friction torque M1 generated by the friction force of the driven shaft support bearing, the transmission mechanism friction torque Mg generated by the friction force of the transmission mechanism, and the drive shaft system friction torque M2 generated by the friction force of the drive shaft support bearing and the support bearing. Assuming the lever arm of the motor support force F1 is L1, then formula (1) can be obtained:

[0036] F1×L1=M0+M1+Mg+M2. (1)

[0037] In formula (1), only the working torque M0 of the measuring disc is proportional to the flow rate of the measured material (i.e., M0 ∝ Coriolis force ∝ material flow rate). Other torques have no regular relationship with the material flow rate, forming interference signals. This is the main reason affecting the measurement accuracy and stability of the Coriolis scale. If the interference forces that generate these torques can be eliminated or most of them can be eliminated, the measurement accuracy and operational stability of the Coriolis scale can be greatly improved.

[0038] The method for counteracting friction in a Coriolis scale provided in this embodiment is applied to a side-mounted Coriolis scale, and the method includes:

[0039] The drive shaft support bearing 1-3 connecting the drive shaft 1-2 is set as the internal bearing of the motor, and the motor support 1-4 connecting the force sensor 1-7 and the base 5 are set as a floating structure that can rotate relative to each other through the bearing, so that the friction force of the drive shaft support bearing becomes an internal force, thereby eliminating the interference of the friction force of the drive shaft support bearing on the force sensor.

[0040] The outer ring of the passive shaft support bearing 2-3, which connects to the passive shaft 2-2, and the base 5 are configured as a floating structure that allows relative rotation. A friction-reducing mechanism is installed between the motor support 1-4 and the outer ring of the passive shaft support bearing 2-3. This mechanism converts the frictional force of the passive shaft support bearing into a tensile force applied to the motor support, thus eliminating the interference of the passive shaft support bearing's frictional force on the force sensor. The motor support and the outer ring of the passive support bearing are flexibly connected via the friction-reducing mechanism, allowing the motor support 1-4 and the outer ring of the passive support bearing 2-3 to rotate slightly around their respective axes due to inertia under the influence of friction.

[0041] The structure for counteracting friction in the Coriolis balance provided in this embodiment is:

[0042] like Figure 1 and Figure 2 As shown, the structure includes a base 5, a drive shaft 1-2, a drive shaft support bearing 1-3, a motor 1-1, a motor support 1-4, a support bearing 1-5, a force sensor 1-7, a passive shaft 2-2, a passive shaft support bearing 2-3, a measuring disk 2-1, a transmission mechanism 3, and a friction force cancellation mechanism.

[0043] The driving shaft and the driven shaft are parallel to each other and spaced apart; the rotor of the motor is coaxially and fixedly connected to the driving shaft, and the motor can drive the driving shaft to rotate; the motor support is fixedly connected to the stator of the motor, and the force sensor is fixedly installed on the motor support through rigid rods 1-8; the measuring disk is coaxially arranged with the driven shaft, and the measuring disk is fixedly connected to the driven shaft.

[0044] A drive shaft support bearing 1-3 is provided between the drive shaft 1-2 and the motor support 1-4. Specifically, the inner ring of the drive shaft support bearing is fixedly connected to the drive shaft, and the outer ring of the drive shaft support bearing is fixedly connected to the motor support.

[0045] A support bearing 1-5 is provided between the motor support 1-4 and the base 5. Specifically, the inner ring of the support bearing is fixedly connected to the motor support, and the outer ring of the support bearing is fixedly connected to the base, so that a floating structure that can rotate relative to each other is formed between the motor support and the base.

[0046] The outer ring of the passive shaft support bearing is fixedly sleeved with a protective shaft 2-4, and a protective shaft support bearing 2-5 is provided between the protective shaft and the machine base. Specifically, the inner ring of the protective shaft support bearing is fixedly connected to the protective shaft, and the outer ring of the protective shaft support bearing is fixedly connected to the machine base, so that a floating structure that can rotate relative to each other is formed between the outer ring of the passive shaft support bearing and the machine base.

[0047] The motor support 1-4 and the sheath shaft 2-4 are connected by a steel wire rope 4, forming a flexible connection between the motor support and the sheath shaft. This allows the sheath shaft to rotate slightly around its own axis due to inertia under the frictional force of the driven shaft support bearing. The steel wire rope and the sheath shaft constitute the friction-counteracting mechanism. In this embodiment, a lower end cover 1-6 of the motor support is fixed to the bottom and sleeved around the outer circumference of the drive shaft; a lower end cover 2-6 of the sheath shaft is fixed to the lower end and sleeved around the outer circumference of the driven shaft; and the two ends of the steel wire rope are respectively fixedly connected to the lower end cover of the support and the lower end cover of the sheath shaft.

[0048] Preferably, the drive shaft support bearing, the support bearing, the passive shaft support bearing, and the sheath shaft support bearing are arranged in two sets, one above the other, to improve the working stability of the Coriolis scale; the drive shaft support bearing, the support bearing, the passive shaft support bearing, and the sheath shaft support bearing are all ball bearings.

[0049] The transmission mechanism connects the drive shaft and the driven shaft. When the motor drives the drive shaft to rotate, the drive shaft drives the driven shaft to rotate synchronously through the transmission mechanism. The transmission mechanism can be a belt drive or a gear drive; in this embodiment, the transmission mechanism is a belt drive.

[0050] This invention can eliminate interference from the following two aspects:

[0051] 1. In the drive shaft system, a drive shaft support bearing is installed between the drive shaft and the motor support, and a support bearing is installed between the motor support and the machine base.

[0052] This structure makes the drive shaft support bearing an internal bearing of the motor. The friction force of the drive shaft support bearing becomes an internal force and will not be transmitted to the force sensor, thus eliminating the interference of the friction force of the drive shaft support bearing on the force sensor.

[0053] Second, a protective shaft is added to the passive shaft system, the passive shaft support bearing is set as a floating structure, and the protective shaft and the motor support are flexibly connected by a steel wire rope. The protective shaft and the steel wire rope form a friction cancellation mechanism.

[0054] During operation, it is assumed that the rotation directions of the drive shaft and the driven shaft are positive. When the material falls onto the measuring plate, in the driven shaft system, the sheath shaft, under the inertial action of the frictional force of the driven shaft support bearing, will generate a positive rotational tendency (i.e., a positive torque due to the frictional force of the driven shaft support bearing). This positive torque will be transmitted to the drive shaft through the transmission mechanism, causing the force sensor to overestimate the measurement result. However, after adding the steel wire rope, a force analysis of the entire drive shaft system shows that under the tension F2 of the steel wire rope, a reverse torque will be applied to the motor support (assuming the lever arm of the steel wire rope is L2, then the tension torque of the steel wire rope is F2 × L2). The force sensor will ultimately detect a decrease in the force acting on the motor support. According to the force balance analysis, the reduced torque of the motor support is equal to the tension torque of the wire rope, which is equal to the friction torque of the passive shaft support bearing. This means that the friction force of the passive shaft support bearing will not be transmitted to the force sensor under the action of the friction force cancellation mechanism, thus eliminating the interference of the friction force of the passive shaft support bearing on the force sensor.

[0055] In summary, by eliminating the interference of friction in the active shaft support bearing and passive shaft support bearing on the force sensor, and because the friction in the support bearing and the sleeve shaft support bearing is very small and negligible, the torque measured by the force sensor is closer to the working torque of the measuring plate, which greatly improves the measurement accuracy and operational stability of the Coriolis scale.

[0056] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A method for compensating friction in a Coriolis scale, applied to a side- mounted Coriolis scale, characterized in that: The method includes: The drive shaft support bearing (1-3) connecting the drive shaft (1-2) is set as the internal bearing of the motor, and the motor support (1-4) connecting the force sensor (1-7) and the base (5) are set as a floating structure that can rotate relative to each other through the bearing, so that the friction force of the drive shaft support bearing becomes the internal force, thereby eliminating the interference of the friction force of the drive shaft support bearing on the force sensor. The outer ring of the passive shaft support bearing (2-3) connected to the passive shaft (2-2) and the machine base are set as a floating structure that can rotate relative to each other through the bearing. A friction force cancellation mechanism is set between the motor support and the outer ring of the passive shaft support bearing so that the friction force of the passive shaft support bearing is converted into a tensile force applied to the motor support through the friction force cancellation mechanism, thereby eliminating the interference of the friction force of the passive shaft support bearing on the force sensor. The motor support and the outer ring of the passive support bearing are flexibly connected by the friction force cancellation mechanism, so that the motor support and the outer ring of the passive support bearing can respectively generate micro-movements around their own axes. The outer ring of the passive shaft support bearing is fixedly fitted with a protective shaft (2-4), and a protective shaft support bearing (2-5) is provided between the protective shaft and the machine base. The motor support (1-4) and the protective shaft (2-4) are connected by a steel wire rope (4). The steel wire rope (4) and the protective shaft (2-4) form the friction force cancellation mechanism. The motor support is fixed with a support lower end cover (1-6) sleeved on the outer circumference of the drive shaft; the lower end of the sheath shaft is fixed with a sheath shaft lower end cover (2-6) sleeved on the outer circumference of the driven shaft; the two ends of the wire rope are respectively fixedly connected to the support lower end cover and the sheath shaft lower end cover.

2. A structure for counteracting friction in a Coriolis scale, comprising a base (5), a drive shaft (1-2), a motor (1-1) driving the drive shaft to rotate, a motor support (1-4) fixedly connected to the motor stator, a driven shaft (2-2) parallel to the drive shaft and spaced apart, a driven shaft support bearing (2-3) with its inner ring fixedly connected to the driven shaft, a measuring disc (2-1) fixedly connected to the driven shaft, and a transmission mechanism (3) connecting the drive shaft and the driven shaft; characterized in that: A force sensor is installed on the motor support; a drive shaft support bearing (1-3) is provided between the drive shaft and the motor support; the inner ring of the drive shaft support bearing is fixedly connected to the drive shaft, and the outer ring of the drive shaft support bearing is fixedly connected to the motor support; the motor support and the machine base are configured as a floating structure that can rotate relative to each other through bearings; the outer ring of the passive shaft support bearing and the machine base are configured as a floating structure that can rotate relative to each other through bearings; a friction force cancellation mechanism is provided between the motor support and the outer ring of the passive shaft support bearing. The outer ring of the passive shaft support bearing is fixedly sleeved with a protective shaft (2-4); a protective shaft support bearing (2-5) is provided between the protective shaft and the machine base; the inner ring of the protective shaft support bearing is fixedly connected to the protective shaft, and the outer ring of the protective shaft support bearing is fixedly connected to the machine base. The motor support and the sheath shaft are flexibly connected by a steel wire rope (4); the steel wire rope and the sheath shaft form the friction force cancellation mechanism; The motor support is fixed with a support lower end cover (1-6) sleeved on the outer circumference of the drive shaft; the lower end of the sheath shaft is fixed with a sheath shaft lower end cover (2-6) sleeved on the outer circumference of the driven shaft; the two ends of the wire rope are respectively fixedly connected to the support lower end cover and the sheath shaft lower end cover.

3. The structure for canceling frictional force in a Coriolis balance according to claim 2, characterized in that: A support bearing (1-5) is provided between the motor support and the machine base; the inner ring of the support bearing is fixedly connected to the motor support, and the outer ring of the support bearing is fixedly connected to the machine base.

4. The structure for counteracting friction in the Coriolis scale according to claim 3, characterized in that: The transmission mechanism adopts belt drive or gear drive.

5. The structure for counteracting friction in the Coriolis scale according to claim 4, characterized in that: The drive shaft support bearing, the support bearing, the passive shaft support bearing, and the sheath shaft support bearing are all ball bearings.

6. The structure for counteracting friction in the Coriolis scale according to claim 5, characterized in that: The active shaft support bearing, the support bearing, the passive shaft support bearing, and the sheath shaft support bearing are respectively arranged in two sets, one above the other, to improve the working stability of the Coriolis scale.

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