Ball screw pair, also known as ball screw pair or ball screw pair. It is composed of two matching parts: a screw and a nut. It is the most accurate and commonly used transmission device in transmission machinery.

brief introduction

When making an object move, it is generally necessary to transmit the motion generated by the power directly or indirectly through other mechanisms to the final motion part. Taking the engine as an example, the combustion of gasoline in the engine causes the piston to move up and down, which is then transmitted to the wheels through the intermediate mechanism to cause rotational motion.

In today's world, all devices that can represent machinery and have various motion mechanisms can be said to have some form of motion transmission mechanism. The ball screw pair is the most reasonable product for converting rotary motion into linear motion, or for converting linear motion into rotary motion.

The ball screw pair is a spiral transmission component with a steel ball as the rolling element between the screw and the nut. It can convert rotational motion into linear motion, or convert linear motion into rotational motion. Therefore, the ball screw pair is not only a transmission component, but also a conversion component between linear motion and rotational motion.

Specialties

Compared to the sliding screw pair, the driving torque is 1/3. Due to the rolling motion of many balls between the screw shaft and the screw nut of the PRTT ball screw pair, it can achieve higher motion efficiency. Compared with the past sliding screw pair, the driving torque reaches less than 1/3, which means that the power required to achieve the same motion result is 1/3 of that of using the sliding screw pair. It is very helpful in a power saving environment.

High precision assurance

The ball screw pair is continuously produced using the world's highest level mechanical equipment made in Japan, especially in the factory environment of grinding, assembly, and inspection processes. Temperature and humidity are strictly controlled, and precision is fully guaranteed due to a sound quality management system.

Micro feed may

Due to the use of ball motion, the ball screw pair has minimal starting torque and does not experience crawling like sliding motion, ensuring accurate micro feed.

No side clearance, high rigidity

The ball screw pair can be pre pressed, as the pre pressure can cause the axial clearance to reach a negative value, thereby obtaining higher rigidity (by applying pressure to the ball in the ball screw, when used in mechanical devices, etc., the repulsive force of the ball can enhance the rigidity of the wire base).

High speed feed may

The ball screw pair can achieve high-speed feed (motion) due to its high motion efficiency and low heat generation.

Loop mode

There are two commonly used loop methods: outer loop and inner loop.

The ball sometimes comes out of contact with the screw during the circulation process, which is called an external circulation; The constant contact with the screw is called internal circulation. Each closed loop of the ball is called a column, and the number of leads contained in each closed loop of the ball is called the number of turns. Each nut of the inner circulation ball screw pair has 2, 3, 4, 5 rows, etc., with only one turn per row; There are several types of outer loops in each column, including 1.5, 2.5, and 3.5 loops.

(1) External circulation: External circulation refers to the process where the ball returns to the screw nut through a spiral groove or tube on the outer surface of the nut and enters the circulation again after the circulation process is completed. The return methods of the external circulation ball screw nut pair during ball circulation mainly include end cover type, insertion tube type, and spiral groove type.

End cover type, a longitudinal hole is machined on the nut to serve as a return passage for the ball. The cover plates at both ends of the nut are equipped with return ports for the ball, which enter the return tube and form a cycle. The plug-in type uses a bent pipe as the return pipe, which has good craftsmanship, but due to the protruding nut outside the pipe, the radial size is relatively large. Spiral groove type, it is a type of structure that milling a spiral groove on the outer circle of the nut, drilling through holes at both ends of the groove and tangential to the threaded raceway to form a return channel. This type of structure has smaller radial dimensions than the plug-in structure, but its manufacturing is more complex. The external circulation ball screw has a simple structure and manufacturing process, and is widely used. Its disadvantage is that the seam of the raceway is difficult to smooth, which affects the smoothness of the ball raceway.

(2) Internal circulation: The internal circulation adopts a reverser to achieve ball circulation, and there are two types of reversers. The cylindrical convex key reverser has a cylindrical part embedded in the nut and a reverse groove at the end. The reverse groove is positioned against the cylindrical outer circular surface and its upper circular key to ensure alignment with the direction of the thread raceway. Flat circular insert reverser, which is a general round headed flat key insert. The insert is embedded in the groove of the nut, and its end is provided with a reverse groove, which is positioned using the outer contour of the insert. Comparing the two types of inverters, the latter has a smaller size, which reduces the radial size of the nut and shortens the axial size. But the precision requirements for the outer contour of this inverter and the groove size on the nut are high.

Construction

The ball screw pair has unique features in the construction of the screw nut part. According to the circulation mode of the ball, it can be divided into

① There is a ball rotation channel between the bent screw pair and the screw nut. The ball generates axial load on the channel, and after rolling around the screw shaft, the ball enters the bend mouth embedded in the screw nut and circulates again towards the load zone along the bend, thus conducting infinite rolling motion. This product is the most diverse and popular product among ball screw pairs, and can be widely used for various purposes.

② Ball return type.

③ End environment style 

Precautions for using ball screw pairs

When using the ball screw pair, the following precautions should be taken: 1. The rolling nut should move within the effective stroke, and if necessary, limit positions should be set at both ends of the stroke to prevent the nut from detaching from the screw shaft and causing the ball to fall off.

2. Due to its high transmission efficiency, the ball screw pair cannot lock itself. When used for vertical transmission, if the weight of the components is not balanced, it is necessary to prevent reverse transmission caused by the weight of the components after the transmission stops or the motor loses power. The anti reverse transmission method can be turbine screw transmission, hydraulic electric brake, and overrunning clutch.