A range extender and assembly method

Abstract

The application provides a range extender and an assembling method, wherein the range extender comprises an engine and a generator; the engine comprises an engine shell and a crankshaft; the generator comprises a rotating shaft, a front rotor, a rear rotor and a stator; the rotating shaft is connected with the crankshaft; the front rotor is connected with the crankshaft; the rear rotor is connected with the rotating shaft; the stator is arranged around the periphery of the rotating shaft and between the front rotor and the rear rotor; the front side of the stator is connected with the engine shell; the front rotor is arranged inside the engine shell; the front rotor and the rear rotor replace structures such as a flywheel, so that the overall axial size is reduced and the assembling process is improved.

Description

Technical Field

[0001] This invention relates to the field of automotive motor and electrical technology, and in particular to a range extender and its assembly method. Background Technology

[0002] Electric vehicles, as a new energy mode of transportation, are characterized by low noise and high energy efficiency. However, due to limitations in the capacity of existing power batteries, long charging times, and short lifespan of fast-charging batteries, pure electric vehicles have short driving ranges and can only be used in locations with charging stations, thus restricting their development.

[0003] Range extenders utilize existing mature engine technology to compensate for the shortcomings of electric vehicles. When the vehicle battery is low, the range extender will automatically start and continue to provide power. It can also automatically start when going uphill or when the electric vehicle is carrying heavy loads, providing energy boost to the electric vehicle battery, preventing over-discharge of the battery and shortening its lifespan, and reducing the incidence of traffic accidents.

[0004] For example, in the range extender generator structure disclosed in CN206211731U, the generator's motor shaft and engine crankshaft are connected via a flywheel. Similarly, in the internal combustion engine of the range extender disclosed in CN111749785A, the motor shaft and crankshaft are connected via a torsional damper. It is evident that the motor shaft and crankshaft are driven by either a flywheel or a torsional damper, resulting in a larger overall axial dimension and reduced assembly efficiency. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a range extender and its assembly method, which solves the issues of large space occupation and high cost of existing range extenders, and effectively improves assembly efficiency.

[0006] According to one object of the present invention, the present invention provides a range extender, comprising:

[0007] An engine, the engine comprising an engine housing and a crankshaft;

[0008] A generator, comprising a shaft, a front rotor, a rear rotor, and a stator, wherein the shaft is connected to the crankshaft, the front rotor is connected to the crankshaft, the rear rotor is connected to the shaft, the stator surrounds the shaft and is located between the front rotor and the rear rotor, the front side of the stator is connected to the engine housing, and the front rotor is located inside the engine housing.

[0009] In a preferred embodiment, the generator further includes:

[0010] The rear end cover is connected to the rear side of the stator, the rotating shaft is rotatably connected to the rear end cover, and the rear rotor is located inside the rear end cover.

[0011] In a preferred embodiment, a bearing is provided between the rotating shaft and the rear end cover.

[0012] In a preferred embodiment, the outer wall of the rotating shaft is provided with a front axle step and a rear axle step, the front end of the rotating shaft is detachably connected to the crankshaft, the front rotor abuts between the crankshaft flange of the crankshaft and the front axle step, and the rear rotor is fixed on the rear axle step.

[0013] In a preferred embodiment, the rotating shaft is integrally connected to the crankshaft, a rear axle step is provided on the outer wall of the rotating shaft, the front rotor is fixed on the crankshaft flange of the crankshaft, and the rear rotor is fixed on the rear axle step.

[0014] According to another objective of the present invention, the present invention provides a method for assembling a range extender, comprising the following steps:

[0015] a. Fix the front rotor to the crankshaft of the engine;

[0016] b. The stator is arranged on the shaft connected to the crankshaft, and the engine housing of the engine is connected to the front side of the stator;

[0017] c. Fix the rear rotor to the rotating shaft so that the stator is located between the front rotor and the rear rotor.

[0018] In a preferred embodiment, after step c, the method further includes:

[0019] A rear end cover is fixed to the rear side of the stator, and the rotating shaft and the rear end cover are rotatably connected so that the rear rotor is located inside the rear end cover.

[0020] In a preferred embodiment, a rear axle step is provided on the outer wall of the rotating shaft, and therefore step c includes:

[0021] The rear rotor is inserted into the shaft from the rear end and fixed on the rear shaft step.

[0022] In a preferred embodiment, the front end of the rotating shaft is detachably connected to the crankshaft, and therefore step a includes:

[0023] a1. Insert the front rotor into the shaft from the front end of the shaft;

[0024] a2. Connect the front end of the rotating shaft to the crankshaft, and fix the front rotor to the crankshaft flange.

[0025] In a preferred embodiment, the front end of the rotating shaft is integrally connected to the crankshaft, and the diameter of the central hole of the front rotor is larger than the outer diameter of the rear axle step. Therefore, step a includes:

[0026] The front rotor is inserted into the shaft from the rear end of the shaft, passes through the rear axle step, and is fixed to the crankshaft flange of the crankshaft.

[0027] Compared with existing technologies, this technical solution has the following advantages:

[0028] The crankshaft and the rotating shaft can be integrated or detachably connected, while omitting the flywheel and torsional damper. Furthermore, the front rotor is housed inside the engine casing, which not only reduces the overall axial dimension but also reduces assembly steps and has advantages such as compact structure and small space occupation.

[0029] The front rotor is connected to the crankshaft, and the rear rotor is connected to the shaft. That is, the front rotor and the rear rotor replace structures such as flywheels, ensuring smooth and reliable operation.

[0030] The front rotor, the rear rotor, and the stator are parallel, meaning the generator is an axial flux motor. Axial flux motors have advantages such as small axial dimensions, compact structure, small size, light weight, and high torque density, thus further reducing the overall axial dimensions.

[0031] The engine has a conventional structure, and the generator is directly mounted on the engine. The generator is assembled from front to back, and the engine and generator are connected to each other to form a range extender, which makes it manufacturable and improves assembly efficiency.

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0033] Figure 1 This is a cross-sectional view of the first embodiment of the range extender described in this invention;

[0034] Figure 2 This is a front view of the first embodiment of the range extender described in this invention;

[0035] Figure 3 This is a schematic diagram of one side of the first embodiment of the range extender described in this invention;

[0036] Figure 4 This is a schematic diagram of the other side of the first embodiment of the range extender described in this invention;

[0037] Figure 5 This is a cross-sectional view of the second embodiment of the range extender described in this invention.

[0038] In the diagram: 100 Engine, 110 Engine Housing, 111 Engine Front Housing, 112 Connecting Housing, 112a Through Hole, 113 Engine Connecting Lug, 120 Crankshaft, 121 Crankshaft Body, 122 Crankshaft Flange, 200 Generator, 210 Shaft, 211 Front Axle Step, 212 Rear Axle Step, 220 Front Rotor, 221 Center Hole, 230 Rear Rotor, 240 Stator, 241 Stator Connecting Lug, 250 Rear End Cover, 251 Reinforcing Rib, 252 Rear Connecting Lug, 260 Bearing, 300 Dust Cover. Detailed Implementation

[0039] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0040] First Embodiment

[0041] like Figure 1 As shown, the range extender includes:

[0042] Engine 100, the engine 100 including engine housing 110 and crankshaft 120;

[0043] The generator 200 includes a shaft 210, a front rotor 220, a rear rotor 230, and a stator 240. The shaft 210 is connected to the crankshaft 120, the front rotor 220 is connected to the crankshaft 120, the rear rotor 230 is connected to the shaft 210, the stator 240 surrounds the shaft 210 and is located between the front rotor 220 and the rear rotor 230, the front side of the stator 240 is connected to the engine housing 110, and the front rotor 220 is located inside the engine housing 110.

[0044] The crankshaft 120 and the rotating shaft 210 are connected, omitting the flywheel and torsional damper. The front rotor 220 is housed within the engine housing 110, reducing the overall axial dimension and assembly steps, while also offering advantages such as compact structure and small footprint. The front rotor 220 is connected to the crankshaft 120, and the rear rotor 230 is connected to the rotating shaft 210. This fully utilizes the structural characteristics of the axial flux motor, replacing the flywheel as a counterweight with the front and rear rotors 220 and 230 of the axial flux motor. This simplifies the structure, reduces the axial dimension, and lightens the overall weight of the range extender, ensuring smooth and reliable operation. The front rotor 220, rear rotor 230, and stator 240 are parallel, meaning the generator 200 is an axial flux motor. Axial flux motors offer advantages such as small axial dimension, compact structure, small size, light weight, and high torque density, further reducing the overall axial dimension.

[0045] like Figure 1 As shown, the front rotor 220 is fixed on the crankshaft 120. Specifically, the crankshaft 120 includes a crankshaft body 121 and a crankshaft flange 122. The front rotor 220 can be inserted into the crankshaft 210 from the front end of the rotating shaft 210. After the front end of the rotating shaft 210 is detachably connected to the crankshaft flange 122, the front rotor 220 is fixed to the crankshaft flange 122 of the crankshaft 120 by bolts.

[0046] The crankshaft body 121 and the crankshaft flange 122 can be connected as a single unit, and the rotating shaft 210 and the crankshaft flange 122 can be connected by means of plug-in, snap-fit, etc.

[0047] like Figure 1 As shown, the outer wall of the rotating shaft 210 is provided with a front axle step 211 and a rear axle step 212. The front rotor 220 abuts between the crankshaft flange 122 of the crankshaft 120 and the front axle step 211, and the rear rotor 230 is fixed on the rear axle step 212.

[0048] In addition to being fixed to the crankshaft flange 122 of the crankshaft 120, the front rotor 220 is also positioned between the crankshaft flange 122 and the front axle step 211, improving the fixing effect. The rear rotor 230 can be inserted into the rotating shaft 210 from the rear end of the rotating shaft 210 and fixed to the rear axle step 212 by bolts.

[0049] like Figure 1As shown, the stator 240 is located between the front rotor 220 and the rear rotor 230, and air gaps are provided between the stator 240 and the front rotor 220 and the rear rotor 230 respectively. The stator 240 can also be inserted into the rotating shaft 210 from the rear end of the rotating shaft 210 and held between the front rotor 220 and the rear rotor 230.

[0050] The stator 240 includes an iron core, windings, and a housing, wherein the windings are sleeved on the iron core and are entirely encapsulated inside the housing.

[0051] The engine housing 110 and the stator 240 can be fixed together by bolts. The outer periphery of the engine housing 110 is provided with a plurality of engine connecting ears 113, and the outer periphery of the stator 240 is provided with a plurality of stator connecting ears 241. The engine connecting ears 113 and the stator connecting ears 241 correspond to each other, and the corresponding engine connecting ears 113 and the stator connecting ears 241 are connected by a first bolt.

[0052] like Figures 1 to 3 As shown, the generator 200 further includes:

[0053] The rear end cover 250 is connected to the rear side of the stator 240, the rotating shaft 210 is rotatably disposed with the rear end cover 250, and the rear rotor 230 is located inside the rear end cover 250.

[0054] The outer surface of the rear end cover 250 is provided with a plurality of reinforcing ribs 251 to improve structural strength. The plurality of reinforcing ribs 251 are arranged at intervals along the circumference. The reinforcing ribs 251 may be V-shaped, but are not limited thereto.

[0055] like Figure 1 As shown, a bearing 260 is provided between the rotating shaft 210 and the rear end cover 250. That is, the generator 200 is equipped with the bearing 260 on only one side, and the other side uses the crankshaft 120 for concentricity to ensure the coaxiality of the front rotor 220, the rear rotor 230 and the stator 240.

[0056] The rear end cover 250 and the stator 240 can be fixed together by bolts, see reference. Figure 2 and Figure 3 The outer periphery of the rear end cover 250 is provided with a plurality of rear connecting ears 252, and the outer periphery of the stator 240 is provided with a plurality of stator connecting ears 241. The rear connecting ears 252 and the stator connecting ears 241 correspond to each other, and the corresponding rear connecting ears 252 and the stator connecting ears 241 are connected by a second bolt.

[0057] The first bolt and the second bolt can be the same bolt, that is, the rear connecting lug 252, the engine connecting lug 113, and the stator connecting lug 241 correspond to each other in sequence and are fixed by the same bolt, thereby improving assembly efficiency. Of course, the first bolt and the second bolt can be staggered.

[0058] The stator 240 is sealed and fixed between the engine housing 110 and the rear end cover 250. The front rotor 220 is connected to the crankshaft 120, and the rear rotor 230 is connected to the rotating shaft 210. Therefore, the relative positions of the front rotor 220, the rear rotor 230 and the stator 240 can be fixed.

[0059] like Figure 1 and Figure 4 As shown, the engine housing 110 includes an engine front housing 111 and a connecting housing 112. The connecting housing 112 has a through hole 112a extending through the front and rear sides. The front side of the connecting housing 112 is connected to the engine front housing 111, and the rear side of the connecting housing 112 is connected to the stator 240. The engine housing 110 also includes an engine rear housing, which is connected to the engine front housing 111.

[0060] The engine front housing 111 is offset above the front side of the connecting housing 112, thus exposing the corresponding through hole 112a below the front side of the connecting housing 112. A dust cover 300 is arranged below the front side of the connecting housing 112 to prevent dust. The dust cover 300 can be fixed by connecting lugs and bolts. The dust cover 300 can be semi-circular and may have reinforcing ribs or other structures.

[0061] The engine 100 has a conventional structure. By redesigning the generator 200, it can be adapted to accommodate different types of engines. The generator 200 is independently assembled, sharing no parts with the engine 100, and requires no modification to the existing engine structure, thus increasing the generator's applicability. The engine 100 can also be an axial flux motor.

[0062] Furthermore, the generator 200 can be independently designed and integrated. The maximum outer diameter of the generator 200 can reach 300mm, its overall axial dimensions can be optimized, and its motor efficiency can be improved. Currently, the axial dimension of the generator 200 is 130mm, and its weight is only 28kg.

[0063] Second Embodiment

[0064] like Figure 5As shown, the range extender in the second embodiment differs from the first embodiment in that the rotating shaft 210 is integrally connected to the crankshaft 120. Since the rotating shaft 210 and the crankshaft 120 are integrally connected, the assembly process is omitted, further improving assembly efficiency. Furthermore, by integrally molding the crankshaft 120 of the engine 100 and the rotating shaft 210 of the generator 200, the assembly process is avoided from affecting the concentricity of the engine and generator, simplifying the assembly process and improving assembly accuracy.

[0065] like Figure 5 As shown, a rear axle step 212 is provided on the outer wall of the rotating shaft 210, the front rotor 220 is fixed on the crankshaft flange 122 of the crankshaft 120, and the rear rotor 230 is fixed on the rear axle step 212.

[0066] The diameter of the central hole 221 of the front rotor 220 is larger than the outer diameter of the rear axle step 212, so that the front rotor 220 is inserted into the crankshaft 210 from the rear end of the crankshaft 210, and the rear axle step 212 passes through the central hole 221 of the front rotor 220, thereby fixing the front rotor 220 to the crankshaft flange 122 of the crankshaft 120. The rear rotor 230 is also inserted into the crankshaft 210 from the rear end of the crankshaft 210 and fixed to the rear axle step 212.

[0067] The rotating shaft 210 and the crankshaft 120 are integrally connected, and the generator 200 weighs 26 kg after removing the rotating shaft 210.

[0068] Third Embodiment

[0069] like Figure 1 As shown, the assembly method of the range extender in the first embodiment includes the following steps:

[0070] a. Fix the front rotor 220 to the crankshaft 120 of the engine 100;

[0071] b. The stator 240 is arranged on the rotating shaft 210 connected to the crankshaft 120, and the engine housing 110 of the engine 100 is connected to the front side of the stator 240.

[0072] c. Fix the rear rotor 230 on the rotating shaft 210 so that the stator 240 is located between the front rotor 220 and the rear rotor 230.

[0073] The engine 100 has a conventional structure, and the generator 200 is directly assembled on the engine 100. The generator 200 is assembled from front to back to obtain the generator 200, and the engine 100 and generator 200 are connected to each other, which makes it manufacturable and improves assembly efficiency.

[0074] like Figure 1 As shown, the front end of the rotating shaft 210 is detachably connected to the crankshaft 120, and therefore step a includes:

[0075] a1. Insert the front rotor 220 into the rotating shaft 210 from the front end of the rotating shaft 210;

[0076] a2. Connect the front end of the rotating shaft 210 to the crankshaft 120, and fix the front rotor 220 on the crankshaft flange 122 of the crankshaft 120.

[0077] The outer wall of the rotating shaft 210 is provided with a front axle step 211. Then, in step a1, the front end of the rotating shaft 210 is inserted into the center hole 221 of the front rotor 220 so that the front rotor 220 is assembled at the front end of the rotating shaft 210, and the rear side of the front rotor 220 is limited by the front axle step 211. When the front end of the rotating shaft 210 is connected to the crankshaft flange 122 of the crankshaft 120, the front rotor 220 is held between the crankshaft flange 122 and the front axle step 211. Finally, the front rotor 220 is fixed to the crankshaft flange 122 by bolts.

[0078] like Figure 1 As shown, in step b, the stator 240 is inserted into the rotating shaft 210 from the rear end of the rotating shaft 210, and the engine housing 110 of the engine 100 is connected to the front side of the stator 240.

[0079] like Figure 1 As shown, a rear axle step 212 is provided on the outer wall of the rotating shaft 210, and therefore step c includes:

[0080] The rear rotor 230 is inserted into the shaft 210 from its rear end, and the rear rotor 230 is fixed to the rear axle step 212. The rear rotor 230 abuts against the rear side of the rear axle step 212 and is fixed with bolts.

[0081] like Figure 1 As shown, after step c, the method further includes:

[0082] The bearing 260 is sleeved at the rear end of the rotating shaft 210;

[0083] The rear end cover 250 is disposed on the outer sleeve of the bearing 260, and the rear end cover 250 is connected to the rear side of the stator 240.

[0084] The rear rotor 230 is located inside the rear end cover 250, and the stator 240 is fixed to the engine housing 110 and the rear end cover 250. At the same time, air gaps are provided between the stator 240 and the front rotor 220 and the rear rotor 230 respectively, and the air gaps can be adjusted according to design requirements.

[0085] The front rotor 220 is assembled at the front end of the shaft 210, while the stator 240, the rear rotor 230 and the rear end cover 250 are assembled sequentially from the rear end to the front end of the shaft 210 to obtain the generator 200. At the same time, the generator 200 and the engine 100 are connected to obtain the range extender.

[0086] Fourth embodiment

[0087] like Figure 5 As shown, the assembly method of the range extender includes the following steps:

[0088] a. Fix the front rotor 220 to the crankshaft 120 of the engine 100;

[0089] b. The stator 240 is arranged on the rotating shaft 210 connected to the crankshaft 120, and the engine housing 110 of the engine 100 is connected to the front side of the stator 240.

[0090] c. Fix the rear rotor 230 on the rotating shaft 210 so that the stator 240 is located between the front rotor 220 and the rear rotor 230.

[0091] Unlike the third embodiment, the front end of the rotating shaft 210 is integrally connected to the crankshaft 120, and the diameter of the central hole 221 of the front rotor 220 is larger than the outer diameter of the rear axle step 212. Therefore, step a includes:

[0092] The front rotor 220 is inserted into the shaft 210 from the rear end of the shaft 210, and is fixed to the crankshaft flange 122 of the crankshaft 120 via the rear axle step 212.

[0093] That is, the front rotor 220, the stator 240, the rear rotor 230 and the rear end cover 250 are assembled sequentially from the rear end to the front end of the rotating shaft 210 to obtain the generator 200. At the same time, the generator 200 and the engine 100 are connected to form the range extender.

[0094] In summary, the crankshaft 120 and the rotating shaft 210 can be integrally formed or detachably connected, eliminating the need for a flywheel and torsional damper. Furthermore, the front rotor 220 is housed within the engine housing 110, reducing the overall axial dimension and assembly steps, while also offering advantages such as compact structure and small footprint. The front rotor 220 is connected to the crankshaft 120, and the rear rotor 230 is connected to the rotating shaft 210; thus, the front rotor 220 and rear rotor 230 replace structures such as the flywheel, ensuring smooth and reliable operation. The front rotor 220, rear rotor 230, and stator 240 are parallel, meaning the generator 200 is an axial flux motor. Axial flux motors offer advantages such as small axial dimension, compact structure, small size, light weight, and high torque density, further reducing the overall axial dimension. The engine 100 has a conventional structure. The generator 200 is directly mounted on the engine 100 and assembled from front to back to obtain the generator 200. At the same time, the engine 100 and the generator 200 are connected to each other to assemble a range extender, which makes it manufacturable and improves assembly efficiency.

[0095] The embodiments described above are only used to illustrate the technical ideas and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The scope of patent application of the present invention should not be limited by these embodiments. That is, any equivalent changes or modifications made in accordance with the spirit disclosed in the present invention still fall within the patent scope of the present invention.

Claims

1. A range extender, characterized in that, include: An engine (100) includes an engine housing (110) and a crankshaft (120). A generator (200) includes a shaft (210), a front rotor (220), a rear rotor (230), and a stator (240). The shaft (210) is connected to the crankshaft (120), the front rotor (220) is connected to the crankshaft (120), the rear rotor (230) is connected to the shaft (210), the stator (240) surrounds the shaft (210) and is located between the front rotor (220) and the rear rotor (230), the front side of the stator (240) is connected to the engine housing (110), and the front rotor (220) is located inside the engine housing (110). The front rotor (220) abuts between the crankshaft flange (122) of the crankshaft (120) and the front axle step (211) of the shaft (210). The crankshaft flange (122) and the shaft (210) are detachably connected. A bearing (260) is provided between the shaft (210) and the rear end cover (250). The rear rotor (230) is embedded in the rear end cover (250). The engine housing (110) includes an engine front housing (111) and a connecting housing (112). The front side of the connecting housing (112) is connected to the engine front housing (111), and the rear side of the connecting housing (112) is connected to the stator (240). The front rotor (220) is located inside the connecting housing (112).

2. The range extender as described in claim 1, characterized in that, The generator (200) also includes: The rear end cover (250) is connected to the rear side of the stator (240), the rotating shaft (210) is rotatably connected to the rear end cover (250), and the rear rotor (230) is located inside the rear end cover (250).

3. The range extender as described in claim 2, characterized in that, A bearing (260) is provided between the rotating shaft (210) and the rear end cover (250).

4. The range extender as described in claim 1, characterized in that, The outer wall of the shaft (210) is provided with a front axle step (211) and a rear axle step (212). The front end of the shaft (210) is detachably connected to the crankshaft (120). The front rotor (220) abuts between the crankshaft flange (122) of the crankshaft (120) and the front axle step (211). The rear rotor (230) is fixed on the rear axle step (212).

5. A method for assembling a range extender, characterized in that, Includes the following steps: a. The front rotor (220) is fixed on the crankshaft (120) of the engine (100), and the front rotor (220) is located inside the connecting shell (112) of the engine housing (110) of the engine (100); b. A stator (240) is arranged on a rotating shaft (210) connected to the crankshaft (120), and the engine housing (110) of the engine (100) is connected to the front side of the stator (240); c. Fix the rear rotor (230) on the rotating shaft (210) so that the stator (240) is located between the front rotor (220) and the rear rotor (230); Step a includes: a1. Insert the front end of the rotating shaft (210) into the center hole (221) of the front rotor (220) so that the front rotor (220) is assembled at the front end of the rotating shaft (210), and the rear side of the front rotor (220) is limited by the front axle step (211); a2. The front end of the rotating shaft (210) is detachably connected to the crankshaft (120), and the front side of the front rotor (220) is fixed on the crankshaft flange (122) of the crankshaft (120); Following step c, the method further includes: A bearing (260) is fitted at the rear end of the rotating shaft (210). A rear end cover (250) is fitted over the bearing (260), and the rear end cover (250) is connected to the rear side of the stator (240).

6. The assembly method of the range extender as described in claim 5, characterized in that, Following step c, the method further includes: A rear end cover (250) is fixed to the rear side of the stator (240), and the rotating shaft (210) and the rear end cover (250) are rotatably connected so that the rear rotor (230) is located inside the rear end cover (250).

7. The assembly method of the range extender as described in claim 5, characterized in that, A rear axle step (212) is provided on the outer wall of the rotating shaft (210), and therefore step c includes: The rear rotor (230) is inserted into the shaft (210) from the rear end and fixed on the rear shaft step (212).

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