KISSsys Instruction 901, Rev. 0

Transcription

1 KISSsys Instruction 901, Rev. 0 Circular power flow, power split gearboxes KISSsoft AG Uetzikon Hombrechtikon Switzerland Tel: Fax: info@kisssoft.ag

2 1 Document information 1.1 Document change record Revision Date Author Comments HD Original document 1.2 Table of content 1 Document information Document change record Table of content References Introduction Summary System data Structure in KISSsys Connections in KISSsys Redefining the kinematics Error message Variables for controlling the power flow Definition of the alternate kinematic calculation Defining a user interface User Interface Running the kinematic function Changing the power distribution Settings for the strength calculations Limitation Considerations for gear z Considerations for the idler gears z2a and z2b Considerations for gear z References [1] KISSsys model KISSsys-ANL ks 2 / 12

3 2 Introduction 2.1 Summary In this document, we will see how a power flow can be divided into two branches that will lager merge again. This kind of power flow split needs to be defined manually using a function explained below, it is not a standard feature in KISSsys. The power flow on the input side can be divided into two branches and the ratio by which the power is distributed into the two branches can be defined. We may define the task of this document as follows: Given is a certain type of gearbox with a power split and merge. We will define a variable to control how the power flow is distributed between the two branches. We will define a function on how to calculate the kinematics of this model. Finally, we check whether the function works as desired. 2.2 System data The gearbox (or the part of the gearbox discussed in this document) consists of a pinion that is driving two idler gears. These two gears are then driving a single output gear. So, there are a total of four gears, arranged in a circle. Most commonly, the input power is split into two equal parts and the two idler gears have the same size as shown in the figure below: Branch 1 of power flow 50% power Pinion, driving Idler gears, driven by the pinion, driving the gear Gear, driven 100% power 100% power Power split on input side 50% power Branch 2 of power flow Power merge on input side Figure Power split and merge with 50%:50% power split in each branch. Idler gears are identical Of course, we can also model systems where each branch has a different power, e.g. 40% and 60%. 3 / 12

4 2.3 Structure in KISSsys In KISSsys, we will use the folllowing structure. There will be four shafts and four gears. The two branches of the power flow will use the index a and index b : Branch 1 of power flow a Shafts s1 s2a s2b s3 Gears z1 z2a z2b z3 Branch 2 of power flow: b Figure Shafts, Gears All these elements will be put inside the group GB. The tree structure in the KISSsys model with the gears and shafts should look like this (of course, you can also add bearings): Figure Tree structure consisting of the group GB, the four shafts and the four gears. 4 / 12

5 2.4 Connections in KISSsys The gear meshes are represented using connections in KISSsys. We use the following connections: gp1a gp2a gp1b gp2a Figure Connections representing the meshes Connection name First gear in connection Second gear in connection gp1a z1 z2a gp1b z1 z2b gp2a z2a z3 gp2b z2b z3 For each connection, add a gear pair calculation. Conveniently, use the the two gear names to form the gear pair calculation name. Then, the KISSsys model and the kinematics will look like this: Figure Left: tree structure of KISSsys model with connections and gear pair calculations added. Right: resulting kinematic. Finally add an input coupling on the shaft s2 and an output coupling on shaft s3. Then add the power input and the power output: 5 / 12

6 Figure Left: tree structure with couplings added on s1 and s3 and power input and output added. Right: kinematic model. For the power input, use 10Nm torque and 10RpM as speed, giving a power of kW. On the output side, you do not need to define any data, it will be calculated: Figure Left: defining the power input. Right: defining the power output. 3 Redefining the kinematics 3.1 Error message If you now want to run the kinematic calculation by using the button as shown below, you will get an error message. KISSsys does not know how to split the power between the two paths, and hence it is not possible to run the kinematic calculation: 6 / 12

7 Figure Kinematic calculation error. 3.2 Variables for controlling the power flow We need to define how much power is going through each branch of the gearbox. For this, we introduce a variable x (of type Real ) in System : Figure Adding a new variable x in System (use right mouse click on System and select New variable ) And we need a variable activated (of type Real ) in the connection gp1b. This is needed to control the kinematic analysis. Add the variable as shown below: Figure Adding a new variable activated in gp1b (use right mouse click on gp1b and select New variable ) 7 / 12

8 Finally, add a variable ModKinematics of type Function in System. This function will be used to execute the kinematic calculation: Figure Adding a variable of type Function, with the name ModKinematic to System (use right mouse click on System and select New variable ) 3.3 Definition of the alternate kinematic calculation The function ModKinematic is now edited as shown below: Figure Function ModKinematic //calculate first kinematic normally System.calcKinematic(); First kinematics will be calculated normally and with this all power will the go through only one activated path (we have used the variable activated to switch off one path above //divide forces by the amount of power share GB.gp1b.f1=GB.gp1a.f1*(1/(1+System.x x)); Then divide power values for connections according to power division factor x 8 / 12

9 GB.gp1b.f2=GB.gp1a.f2*(1/(1+System.x)); GB.gp1a.f1=GB.gp1a.f1-GB.gp1b.f1; GB.gp1a.f2=GB.gp1a.f2-GB.gp1b.f2; GB.gp2b.f1=GB.gp2a.f1*(1/(1+System.x)); GB.gp2b.f2=GB.gp2a.f2*(1/(1+System.x)); GB.gp2a.f1=GB.gp2a.f1-GB.gp2b.f1; GB.gp2a.f2=GB.gp2a.f2-GB.gp2b.f2; ksys_refresh(); System.kSoftCalculate(); ksys_refresh(); Power share value is defined under variable x. Gear connections gp1a and gp2a belong to active path. Refresh everything Do the strength calculation 4 Defining a user interface 4.1 User Interface In the user interface, add a reference so you can enter x : Figure Add a reference to x in the user interface. Add 1 so that both branches get the same amount of power. Also, add a function to call the function ModKinematic : Figure A function in the user interface to call the function ModKinematics 4.2 Running the kinematic function Now, double click on Modified Kinematics in the user interface. The kinematics is now being calculated and the schematic will look like this: 9 / 12

10 Figure Schematic after successful calculation of kinematics Go to the KISSsoft calculations for the four meshes to check that each has half of the power (Input power is kW, hence, the power per mesh should be kW/2=0.0052kW). You can check in all four calculations to find: Figure Check the power in the tab Rating in the gear calculatios. 4.3 Changing the power distribution If you now set x=2 in the user interface, you can find that the power in branch a is two times as high as in branch b : Figure Power per mesh. 5 Settings for the strength calculations 5.1 Limitation The below settings are true if the torque distribution is 50% for each branch. 5.2 Considerations for gear z1 If the gear z1 rotates once, each tooth will be in mesh twice. Once with the gear z2a and once with the gear z2b. Both times, the same load level will be applied as in each mesh, 50% of the power is transmitted. To define that the gear z1 sees two load cycles per revolution, go to the KISSsoft calculation z1z2a, go to tab Rating, press button Details and select: 10 / 12

11 Figure Define that for the first gear (which is z1 in our case) the number of load cycles per revolution is 2. Do this also for the KISSsoft calcualtion z1z2b. 5.3 Considerations for the idler gears z2a and z2b The two idler gears teeth will experience alternating bending. First, they will experience the load on one flank (when in mesh with z1) and later on the other flank (when in mesh with z3), giving an alternating bending action per revolution. To consider this, go to the tab Factors in all four calculations and set the factor YM to 0.7. For the meshes with z1, set the factor for gear 2 to 0.7 (in these meshes, the idler gears are gear 2). For meshes with z3, set the factor for gear 1 to 0.7 (now, the idler gear is gear 1) 11 / 12

12 Figure The idler gears are gear 2 (when in mesh with gear 2), they experience alternating bending, set YM=0.7 Figure The idler gears are gear 1 (when in mesh with z3), set for gear 1: YM= Considerationss for gear z3 The same idea as for gear z1 applies. For the calculations z2az3 and z2bz3, use the following setting (now for gear 2 as the gear z3 is the second gear in the mesh): Figure Define that the second gear in the mesh (=z3) experiences two load cycles per revolution. 12 / 12