worm and worm wheel gearbox pdf

Worm And Worm Wheel Gearbox Pdf

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Published: 23.05.2021

Worm drive

Experimental investigations on different worm gears were conducted on several test rigs, taking into consideration the influence of different gear ratios, worm wheel materials, lubricants, and contact pattern on efficiency and load-carrying capacity.

Recommendations for an increase in overall worm gearbox efficiencies are presented. Due to a wide range of properties, worm gears are an indispensable element on the current transmission market. Furthermore, worm gears provide the opportunity of self-locking, respectively self-braking. Despite these benefits, as a result of greater energy awareness, the efficiency of worm gears is in focus.

Because of high sliding velocities, especially at high gear ratios, gearing losses are a main topic of interest. Other gearbox concepts with combined spur and bevel gear sets show smaller gear ratio fields, and therefore the realization of high gear ratios in only one stage is not possible.

Consequently, fewer components are necessary for worm gearboxes, which allows savings of assembly and maintenance costs. Equation 1. In the case of oil-lubricated worm gears, the gearing losses P VZ are mainly responsible for high overall power losses P V β€” in particular, at low speeds and high torques. High overall power losses are explained by a high sliding motion rate between worm and worm wheel. In order to reduce gearing losses of worm gears, an ideal combination of geometry and material pairing, as well as lubrication and operating conditions, has to be chosen.

Therefore, it is necessary to know to what extent these parameters influence the efficiency of worm gears. Numerous projects have been carried out in recent years and are constantly in progress. Within these research projects, various experimental and theoretical investigations have been executed on worm gears with different sizes, materials, lubricants, and test conditions.

In the scope of this paper, all experimental and theoretical results of this project regarding overall gearbox efficiency are presented in detail. Furthermore, these results are compared to the insights of other research projects.

Thereby, the influence of different worm gear geometries, materials, and lubricants, as well as lubrication and operating conditions on efficiency, is considered. For the experimental investigations, several worm gear test rigs, designed and constructed by FZG, are available. Figure 1 shows a photo and the general principle of this FZG large-sized worm gear test rig. The essential component of this test rig is the test gearbox.

In this gearbox, the investigated worm gear is situated. The test worm wheel is driven by the test worm shaft with a certain input speed n 1. The worm wheel is connected to a reverse transfer gearbox with identical geometry driven by the worm wheel. This connection is realized using a double-joint coupling. In order to load the worm wheel of the test gearbox with a certain output torque T 2 , a hydrostatic torque motor is connected to the reverse transfer gearbox.

This hydrostatic torque motor infinitely adjusts the respective load. The bracing cycle of the test rig is closed by a summation gearbox. Consequently, the direct current motor only has to feed in the occurring overall power losses. These are measured continuously by torque-measuring shafts at input and output of the investigated worm gearbox see Figure 1.

The used torque-measuring shafts have a measuring accuracy of 0. Wear and pitting load-carrying capacity analysis are executed regularly. Results regarding pitting load-carrying capacity are obtained by the assessment of periodically documented flank pictures of the worm wheel.

To measure wear on the investigated worm wheel, a transmission error measuring system see Figure 1 is used. The investigated worm gearboxes are cylindrical worm gears with flank form ZI right-handed thread.

In Table 1, all important gear data of the investigated test gearboxes is listed. The investigated worm gears are made of case-hardened steel worms 20MnCr5 and centrifugally casted copper-tin bronze worm wheels with nickel CuSn12Ni2-C-GZ. The experimental investigations are carried out at various input speeds n 1 and output torques T 2. This serves to evaluate wear and pitting load capacity as well as efficiency of worm gears of this size at different operating conditions.

The gained results are used to verify current calculation methods for worm gears in the German Standard DIN [1]. The conducted test program in the scope of this project [2] is shown in Table 2.

Altogether, four tests are executed at the flanks fore and rear flanks of two worm gears. To smooth tooth flanks and enlarge the contact pattern, a running-in is carried out at the beginning of each test. Figure 3: Development of contact pattern and efficiency during running-in [5, 6] The influence of different lubricants on wear load-carrying capacity and efficiency during running-in is evaluated by testing diverse oils see Table 2.

Furthermore, in test 4, a different oil type is utilized. In the present project with large-sized worm gears, running-in lasts approximately between and hours. After the running-in process, the main test run takes place. For the main tests, two different input speeds are examined to estimate wear behavior and its influence on pitting development.

To analyze wear behavior of this kind of large-sized worm gear, regular measurements are carried out during the main test run with the transmission measuring system see Figure 1. Each wear measurement during test runs lasts exactly one hour. Table 3 gives an overview of all measurement conditions for the documentation of overall gearbox efficiency during running-in and the main test run.

In the following section, the results of all executed tests on large-sized worm gears in the course of this research project [2] are introduced and explained in detail. At the same time, the influence of various factors on overall gearbox efficiency is described in particular.

These influencing factors concern operating and lubrication conditions, geometry, and material. During the experimental investigations, the influence of varying sizes of contact pattern on efficiency is considered in detail as well. For the determination of the contact area f t , all worm wheel flanks are photographed regularly. The evaluation of the contact pattern development of each flank is performed with a specially developed, color-based MatLab program.

At the beginning of the experimental investigations, the contact pattern of each test is adjusted. All initial contact patterns are shown in Table 4. Each contact area f t corresponds to the mean contact area of all worm wheel flanks of one test. On average, both tests on the fore flank tests 1 and 4 show contact areas of 65 to 75 percent. On the rear flank tests 2 and 3 , an average contact area of 60 percent is documented. This causes an enlargement of contact. In the case of test 1, which is exemplarily shown in Figure 2, first efficiency measurements measurement condition 1 are carried out after 0.

This leads to an initial overall gearbox efficiency of As with the contact pattern, an increase in overall gearbox efficiency from After an additional 0. This conclusion corresponds to the results made by [5] and [6] see Figure 3. With an increasing contact area, the overall gearbox efficiency improves during the running-in of worm gears.

Besides the enlargement of the contact area, running-in is accompanied by a smoothing of gear flanks. The roughness of the worm wheel flanks adjusts to the roughness of the worm flanks. It is therefore essential to have low worm flank roughness in order to reduce the coefficient of friction and therefore power losses. The degree of losses is the ratio of overall power losses P V to driving power P 1 β€” the higher the degree of losses, the lower the overall gearbox efficiency see Equation 1.

The share of gearing losses P VZ decreases due to lower coefficients of friction. For the other losses, there is no dependence of the arithmetic mean roughness Ra. The sealing losses P VD contributes the smallest share of degree of losses. Next to the size of contact area, the position of contact pattern can influence efficiency.

According to Niemann and Winter [5], contact patterns positioned at inlet side cause higher power losses than contact patterns at outlet side. Wakuri [6] measured about 6 percent lower efficiencies for worm gears with contact patterns positioned at inlet side than with contact patterns at outlet side.

This is explained by higher coefficients of friction at inlet side. With a decreasing ratio, the coefficient of friction decreases as well [5]. Next to this, SNETRA [8] delivers a course of contact lines, contact pattern under load and no-load, as well as distribution of equivalent radius of curvature, Hertzian stresses, and lubricant film thickness.

It is also possible to simulate complete and incomplete contact patterns. Figure 5 shows the results regarding the amount of sum velocities left and sliding velocities right achieved for test 1. Higher coefficients of friction at inlet side than those at outlet side are explained by lower sum velocities at this side of the worm wheel see Figure 5.

In the area where low sum velocities occur, low lubricant film thicknesses arise. Thus, worm gears with contact patterns at outlet side show better efficiencies. The distribution of lubricant film thickness is illustrated in Figure 6. Further measurements during test 1 result in similar values between This is explained by lower sum velocities and an unfavorable lubrication film formation. Lower sum velocities lead to an increase in coefficient of friction and therefore to a decrease in efficiency.

The high influence of input speed on worm gearbox efficiency is considered as well in DIN [1]. Hereby, lower speeds lead to higher degrees of losses. The share of gearing losses P VZ increases due to higher coefficients of friction with lower input speeds. Consequently, large-sized worm gears have a similar behavior regarding the influence of input speed on overall gearbox efficiency. Next to speed, the present output torque T 2 influences the overall efficiency of worm gears [5].

Usually, lower loads lead to lower efficiency values [5]. In the scope of this project [2] with large-sized worm gears, the same behavior is documented. The absolute values of the no-load losses P V0 and the sealing losses P VD are not influenced by the output torque.

US20110247440A1 - Worm gear clutch mechanism - Google Patents

A worm gear is a gear consisting of a shaft with a spiral thread that engages with and drives a toothed wheel. Worm gears are an old style of gear, and a version of one of the six simple machines. Basically, a worm gear is a screw butted up against what looks like a standard spur gear with slightly angled and curved teeth. It changes the rotational movement by 90 degrees, and the plane of movement also changes due to the position of the worm on the worm wheel or simply "the wheel". They are typically comprised of a steel worm and a brass wheel. Figure 1.


Miter Gears. Bevel Gears. Screw Gears. W orm. Gear Pairs. Bevel. Gearboxes. Other. Products. Worms. K W G DL 2 - R1. Hand thread & Number of Starts.


Worm gears: What are they and where are they used?

Compact style also available. This catalog is a supplement to the standard red Bonfiglioli metric catalogs. When evaluating an application, it is recommended that final selections be reviewed by Bonfiglioli personnel. As this is a supplement, refer to the metric catalogs R4 for more detail in regards to each gearbox and gearmotor. Description Ac [lbs] Calculated thrust load [lbs] Rated thrust load - Adjusting power factor - Service factor - Thermal correction factor - Transmission ratio - Intermittence [Ib-ft2] Load moment of inertia [Ib-ft2] Mass moment of inertia for motor [Ib-ft2] Mass moment of inertia for gearbox - Acceleration factor of masses - Radial load stress factor [lb-in] Brake torque [lb-in] Torque [lb-in] Calculated torque [lb-in] Speed reducer rated torque [lb-in] Torque required [rpm] Speed [hp] Power [hp] Calculated power [hp] Motor rated power.

They are also the smoothest, quietest form of gearing when properly applied. Boston Gear offers worm gears manufactured from a variety of materials, such as acetal, minlon, bronze, and cast iron to suit your application's requirements. Note: Because the efficiency of a worm gear drive depends on the lead angle and number of starts on the worm, the ratio should be kept low.

Worm drive

A worm gear clutch mechanism comprising a worm shaft 10 , an output shaft 16 having a worm wheel 11 , and means to move the worm shaft relative the worm wheel, the worm shaft being movable about a tilt axis that is substantially perpendicular to the longitudinal axis of said worm shaft 10 so that the worm shaft is movable into and out of engagement with the worm wheel.

Worm Gears Explained

Experimental investigations on different worm gears were conducted on several test rigs, taking into consideration the influence of different gear ratios, worm wheel materials, lubricants, and contact pattern on efficiency and load-carrying capacity. Recommendations for an increase in overall worm gearbox efficiencies are presented. Due to a wide range of properties, worm gears are an indispensable element on the current transmission market. Furthermore, worm gears provide the opportunity of self-locking, respectively self-braking. Despite these benefits, as a result of greater energy awareness, the efficiency of worm gears is in focus. Because of high sliding velocities, especially at high gear ratios, gearing losses are a main topic of interest.

Experimental investigations on different worm gears were conducted on several test rigs, taking into consideration the influence of different gear ratios, worm wheel materials, lubricants, and contact pattern on efficiency and load-carrying capacity. Recommendations for an increase in overall worm gearbox efficiencies are presented. Due to a wide range of properties, worm gears are an indispensable element on the current transmission market. Furthermore, worm gears provide the opportunity of self-locking, respectively self-braking. Despite these benefits, as a result of greater energy awareness, the efficiency of worm gears is in focus.


CHML WORM GEARBOXES WITH TORQUE LIMITER page Design features - Dimensions page CH WORM GEARED MOTORS AND WORM GEAR.


Worm gears are found in industrial applications, heavy equipment, and even consumer applications. Although their efficiency is relatively low, they can provide very high reduction ratios and, in many cases, are self-locking. Worm gears are constructed of a worm and a gear sometimes referred to as a worm wheel , with non-parallel, non-intersecting shafts oriented 90 degrees to each other. The worm is analogous to a screw with a V-type thread, and the gear is analogous to a spur gear. Like a ball screw , the worm in a worm gear may have a single start or multiple starts β€” meaning that there are multiple threads, or helicies, on the worm.

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A worm drive is a gear arrangement in which a worm which is a gear in the form of a screw meshes with a worm gear which is similar in appearance to a spur gear.

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reduction at input. Worm Gear Boxes Product Spectre. Single stage worm gearboxes. A simple and economical solution for most industrial application. Size 30 -.

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