KISSsys Instruction 902, Rev. 0 Including a torque converter or CVT path in the kinematic model KISSsoft AG Uetzikon 4 8634 Hombrechtikon Switzerland Tel: +41 55 254 20 50 Fax: +41 55 254 20 51 info@kisssoft.ag www.kisssoft.ag
1 Document information 1.1 Document change record Revision Date Author Comments 0 14.2.2014 HD Original document 1.2 Table of content 1 Document information... 2 1.1 Document change record... 2 1.2 Table of content... 2 1.3 References... 2 2 Introduction... 3 2.1 General modeling technique... 3 2.2 Typical arrangement for torque converter... 3 2.3 Principle of a KISSsys model... 4 3 KISSsys model... 5 3.1 Administrator mode... 5 3.2 Settings... 5 3.3 Setting for speed and torque... 6 3.4 Conditions for torque on output side of converter... 7 3.5 Conditions for speed on output side of converter... 8 3.6 Kinematics... 8 4 Modifications... 8 4.1 An example for a torque converter... 8 4.2 Modelling in KISSsys... 9 4.3 User interface... 9 1.3 References [1] KISSsys model KISSsys-ANL13--902.ks [2] KISSsys model KISSsys-ANL-13-902-mod.ks 2 / 10
2 Introduction 2.1 General modeling technique In this document, we will see how a power flow can modeled including a torque converter or a CVT path. Basically, we want to model the kinematics such that we have an input speed and an input torque and we want to have another output speed and output torque. The ratio can vary. If we look at this in a schematic way, we can think of it as follows: Speed 1 Torque 1 Efficiency eta Ratio i Speed 2 Torque 2 So, if we want to model a torque converter, we could for example use the vane angle (alpha) to control the efficiency (eta) and the ratio (i) and a slip (s). Then, eta, i and s would be a function of alpha Then, the schematic would be: Speed 1 Vane angle alpha Speed 2 Torque 1 Torque 2 And the condition would be: Torque 2=i(alpha)*Torque 1*eta(alpha); Speed 2=Speed 1/i(alpha)-slip(alpha) In a generic way, it is shown how to define a relationship between two power elements in KISSsys (ksysspeedorforce Element). The procedure may be used to model - CVT - IVT - Torque converter 2.2 Typical arrangement for torque converter Typically, we have a power source (the motor / it s crank shaft), followed by the torque converter which is driving a transmission. The purpose of the torque converter is to take up the motor speed n1 and torque T1 and deliver a different speed n2 and torque T2 to the transmission. The transmission then converts this speed n2 and torque T2 to the output speed nout and output torque Tout. The torque converter converts n1 and T1 to n2 and T2 following some rules, typically as a function of the vane angle. For example, the efficiency of the converter and it s current ratio is a function of the vane angle, so is the slip of the torque converter. Motorshaft n1 T1 Torque converter n2 T2 Transmission nout TOut 3 / 10
Figure 2.2-1 Principle arrangement of a torque converter In our example, the following conditions apply n2=n1/ratio T2=T1*ratio*eta ratio is the ratio of the converter or CVT path eta is the efficiency of the converter or CVT path 2.3 Principle of a KISSsys model Note [1] In a KISSsys model, we can model the motor as a shaft s1 with a coupling ctc1 and a power output. This power output includes n1 and T1. Then, we have a shaft s2 and a shaft s3 connected by a gear mesh, this is to represent the geared part of the transmission. From the shaft s3 we use a power output Output where we will find nout and TOut. On the shaft s2 we use a coupling ctc2 where a power source TC2 is attached, here we will find n2 and T2. The power source TC2 is fed by TC1, the power output from shaft s1. Between TC1 (which is like the input side of the torque converter) and TC2 (which is like the output side of the converter), we will define a relationship between n1, T1, n2 and T2. Of course we need a power source Input (this is like the piston where the torque is generated) which drives the shaft s1 (which is like the crank shaft). Figure 2.3-1 KISSsys schematic and tree structure KISSsys Element Power element Input Shaft s1 Shaft s2 Shaft s3 Coupling cin on shaft s1 Coupling ctc1 on shaft s1 Corresponds to The power source, like the piston driving the crank shaft The crank shaft The shaft to which the output side of the converter is attached, the first shaft in the geared part of the transmission. A shaft inside the transmission / the output shaft of the transmission To accept the power from Input onto the shaft s1 The connection between the crank shaft of the motor to the input side of the torque converter 4 / 10
Coupling ctc2 on shaft s2 Coupling cout on shaft s3 Power element TC1 Power element TC2 Power element Output Gear z1 on s2 and z2 on s3 The connection between the torque converter and the transmission The coupling for the power output from the transmission The input side of the torque converter The output side of the torque converter The output of the transmission To represent the geared part of transmission Figure 2.3-2 Use of symbols in KISSsys model 3 KISSsys model Use file [1] 3.1 Administrator mode Note that you need to be in administrator mode to do the below changes. 3.2 Settings Under System in the tree structure, use Dialog and select Iteration for speed and torque. This will then ensure that the iteration is performed to find the correct speed and torque data in the whole model, including any functions that we have added (see below) to determine n2 and T2 from n1 and T1: Figure 3.2-1 Required settings in System/Dialog Also, we will use two variables eta and ratio. These, we will add to the group GB. They are of type Real. Use right mouseclick on GB and select New variable. Add the two variables ratio and eta as shown below and assign the values ratio=0.20 and eta=0.50. 5 / 10
Figure 3.2-2 Adding the variables "ratio" and "eta" to the group "GB" 3.3 Setting for speed and torque We want to define / calculate the speed and torque on the output side of the converter. So, for the force element TC2, we need to select that both speed and torque are constrained: Figure 3.3-1 Constrain speed and force (do not enter numerical values, they will be calculated) Note the settings for the input Input, Output and TC1 as below: Figure 3.3-2 Settings for the power input in Input. Here we constrain the speed and the torque and enter a speed and torque value. 6 / 10
Figure 3.3-3 Settings for the output. Both speed and torque on the output are calculated. Figure 3.3-4 Settings for the input side of the torque converter TC1. The speed and torque are calculated by KISSsys. The speed is the same as the input speed (n1=input speed) and the torque is the negative of the input speed (T1=- Input torque). 3.4 Conditions for torque on output side of converter In TC2, we will define the torque on the output side of the torque converter. So, we go to the properties window of the output side of the torque converter (right mouse click on the power element TC2 and select Properties window ). There, we define a formula to calculate the torque T2 from the torque T1 (note that the two torques have opposite sign): Figure 3.4-1 Editing TC2 7 / 10
Figure 3.4-2 Example formula to calculate T2 from T1. Torque T1 is T1=T2*ratio*eta. 3.5 Conditions for speed on output side of converter In TC2, we add a formula to calculate speed n2 from sped n1: Figure 3.5-1 Example formula to calculate n2 from n1. Speed n2 is n1*ratio 3.6 Kinematics Out input speed is 10RpM and our input torque is 10Nm in this example. The ratio is i=0.2 and the efficiency is eta=0.5. We expect as an output speed 10RpM*0.2=5RpM and for the output torque 10Nm/0.2*0.5=25Nm and find the same values in Output : Figure 3.6-1 Results on the output side. 4 Modifications See file [2] 4.1 An example for a torque converter So, if we want to model an example torque converter, we could use the following parameters (the vane angle can be between 0deg to 45deg. At 0deg, no power is transmitted, the output speed is zero (n2=0). At 45deg, maximum power is transmitted): Vane angle, [deg] alpha Efficiency eta=f(alpha) Ratio i=f(alpha) Slip s=f(alpha, n1) Input speed n1 8 / 10
Input torque Output speed Output torque eta=alpha^2/2025*0.95 i=alpha/45 s=n1/25 n2=n1*i-s T2=T1/i*eta T1 n2 T2 The maximum efficiency is 95% and it reduces with lower vane angles If the vane angle is maximised, then, the ratio is 1:1, otherwise, it is less The converter has 4% slip The output speed is the input speed times a ratio (which is not more than 1.00) minus the slip The output torque is higher than the input torque (by 1/i) but we loose some torque due to the efficiency (eta<1) So, we find: n2=n1*alpha/45-n1/25=n1(alpha/45-1/25) T2=T1/(alpha/45)*alpha^2/2025*0.95=T1*alpha/45*0.95 4.2 Modelling in KISSsys We need to add a variable alpha into the group GB and then we can define the torque and speed on TC2 as follows: Figure 4.2-1 Another formula to define the speed as a function of the vane angle alpha. Figure 4.2-2 Another formula to calculate T2 from T1 as a function of the vane angle alpha 4.3 User interface We can now use a user interface to enter the vane angle, input speed, input torque, run the calculation and see the results. Note that 9 / 10
The efficiency is calculated as Output.power/input.power and the ratio is calculated as Input.speed/Output.speed : Figure 4.3-1 User interface for the kinematics 10 / 10