Abstract:
The present invention provides an engine testing apparatus capable of accurately conducting a simulation of a vehicle and includes a dynamometer connected to an output section of an engine under test, a dynamo controller for controlling rotation of the dynamometer, and an actuator for controlling a throttle opening degree of the engine. The dynamo controller and the actuator are controlled to adjust an output of the engine under test, wherein a constant speed driving slip ratio (S a ) in a constant speed running state in a target vehicle speed pattern, an acceleration driving slip ratio (S b ) in an acceleration running state, and a deceleration driving slip ratio (S c ) in a deceleration running state are previously computed as data for correcting tire slippage of the actual running vehicle.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an engine testing apparatus. 
     DESCRIPTION OF THE PRIOR ART 
     As an apparatus for checking performance of an automobile engine, there exists an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test, a dynamo controller for controlling the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test. The engine testing apparatus controls the dynamo controller and the actuator to adjust the output of the engine under test. 
     FIG. 3 schematically shows a general structure of the engine testing apparatus. In FIG. 3, reference numeral  1  represents an engine under test and reference numeral  2  represents a dynamometer. An output shaft  1   a  of the engine  1  and a driving shaft  2   a  of the dynamometer  2  are coupled to each other through a clutch  3  such that the shafts  1   a  and  2   a  can be connected to and disconnected from each other. Reference numeral  4  represents a clutch actuator for driving the clutch  3 . Reference numeral  5  represents a throttle of the engine  1  under test, and the throttle  5  is driven by a throttle actuator  6  and its throttle opening degree is controlled. Reference numeral  7  represents a dynamo controller for controlling the dynamometer  2 . Reference numeral  8  represents a torque sensor mounted to the driving shaft  2   a  of the dynamometer  2 , and reference numeral  9  represents a torque amplifier for appropriately amplifying the output of the torque sensor  8 . 
     Reference numeral  10  represents a control computer as a simulator for controlling the entire apparatus, and reference numeral  11  represents a signal conditioner unit. The computer  10  performs a computation based on an input from an input apparatus (not shown) and based on signals from various sensors such as the torque sensor  8  provided in the apparatus, and outputs commands to various portions of the apparatus. For example, a target vehicle speed pattern  12  shown in FIG. 3, a target vehicle speed pattern  12   a  shown in FIG.  4 (A) or a target vehicle speed pattern  12   b  shown in FIGS. 2 and 6 are inputted to the computer  10 . That is, in each of the target vehicle speed patterns  12 ,  12   a  and  12   b , the horizontal axis shows time (second) and vertical axis shows speed (km/h), and these patterns are target running patterns of desired driving. 
     The signal conditioner unit  11  is an interface having an AD converting function and a DA converting function. The AD converting function of the signal conditioner unit  11  converts signals from various sensors such as a torque sensor  8 . The DA converting function converts commands from the computer  10 , and output commands to various portion of the apparatus such as the dynamo controller  7 , the clutch actuator  4  and the throttle actuator  6 . 
     In a conventional engine testing apparatus, as shown in FIGS. 5 and 9, the moment of inertia of the engine is used to compute the load of rotating objects of an actual vehicle, i.e., an engine, a transmission, a differential gear and tire. This is because the moment of inertia of the engine is greater than moments of other rotating objects. 
     FIGS. 5 and 9 respectively show a conventional control flow and computation flow for the above-described engine testing apparatus. First, the control flow is described. In FIG. 5, reference numeral  13  represents a target pattern generator. The target pattern generator  13 , which is provided in the computer  10 , outputs a target speed signal V, to allow the engine  1  under test to run in a predetermined running pattern based on the target vehicle speed patterns  12 ,  12   a  and  12   b  which have been inputted into the computer  10 . The target speed signal V, is inputted to a rotation control system  14  and a simulation vehicle control system  15 . 
     The rotation control system  14  and the simulation vehicle control system  15  are constituted in the following manner. First, the rotation control system  14  comprises a rotation generator  16  to which the target speed signal V, is inputted, a delay correcting circuit  17 , a butt portion  18 , a rotation feedback controller  19  and the dynamometer  2 . When the target speed signal V r  is inputted to the rotation generator  16 , an engine target rotation number signal [a target value of the dynamometer rotation number (the rotation number, hereinafter)] R r  is outputted from the rotation generator  16  based on the target speed signal V r . 
     For example, as shown in FIG.  4 (B), a target rotation number signal R r  which is converted from the target vehicle speed pattern  12   a  shown in FIG.  4 (A) is obtained in simulation. That is, an engine rotation pattern  33  is obtained. Similarly, when the target vehicle pattern  12   b , is employed, an engine rotation pattern  30 , which is converted from the target vehicle speed pattern  12   b  is obtained as shown in FIG.  6 . When the pattern is converted from target vehicle speed pattern  12   a  to the engine rotation pattern  33  or from the target vehicle speed pattern  12   b  to the engine rotation pattern  30 , a diameter of a tire, a final-drive ratio and a gear ratio in accordance the type of vehicle are taken into consideration. 
     Referring back to FIG. 5, the target rotation number signal R r  becomes a control target rotation number signal R ctl  through the delay correcting circuit  17 , and is outputted to the butt point  18 . Since an actual rotation number signal R a  of the dynamometer  2  has been inputted to the butt point  18 , a deviation Re between the control target rotation number signal R ctl  and an actual rotation number signal R a  is PI-controlled, for example, by the rotation feedback controller  19 , thereby setting an operation amount signal Ud′. The operation amount signal Ud′ is sent to the dynamometer  2 . 
     In FIG. 5, the simulation vehicle control system  15  includes a torque generator  20  to which the target speed signal V r  is inputted and further includes a butt point  21  to which the target speed V r  is inputted and a speed feedback controller  22  are connected in parallel to a rear stage of the target pattern generator  13  which outputs the target speed signal V r . A torque control system  27 , which comprises an adding point  23 , a butt point  24 , a throttle map  25 , a throttle opening degree controller  26  and the engine  1  under test, is provided in the rear stage of the torque generator  20  and the speed feedback controller  22 . A simulation vehicle model  28  is provided in the rear stage of the torque control system  27 . The throttle map  25  is a map for determining a target throttle opening degree to control the engine. The simulation vehicle model  28  is a model for calculating a driving force of the vehicle using the engine output torque to convert the calculated value into a speed signal using the driving force. 
     In the simulation vehicle control system  15 , if the target speed V r  is inputted to the torque generator  20 , a feedforward torque T ff , which is an output torque required for the engine from the torque generator  20 , is outputted to the adding point  23 . In this case, when the target vehicle speed pattern  12  or the target vehicle speed patterns  12   a  and  12   b  is converted into the feedforward torque T ff , a vehicle inertia weight and running resistance in accordance with the type of vehicle are taken into consideration. 
     The target speed signal V r  is butted against an actual speed signal V a  outputted from the simulation vehicle model  28  at the butt point  21 . A deviation there between is sent to the speed feedback controller  22 , and it is outputted to the adding point  23  as a feedback torque T fb . The feedforward torque T ff  and the feedback torque T fb  are added in the adding point  23 , and the target control torque signal T ctl  is obtained. The target control torque signal T ctl  is butted against an actual output torque valve T a  of the engine  1  under test, a deviation T e  thereof is inputted to the throttle map  25 . An operation target throttle opening degree θ is obtained. The operation target throttle opening degree θ is input to the throttle opening degree controller  26 , an operation amount U a  is set, and the operation amount signal U a  is sent to the engine under test  1 . 
     Next, the computation flow is explained. In FIG. 9, reference numerals  49  and  50  respectively represent a torque computation system and a rotation computation system. The torque computation system  49  comprises a butt point  51  for butting the output torque value T a  of the engine  1  under test and a torque value T E  resulting from an engine inertia moment J e  against each other, a multiplier  52  for multiplying the output T 1  of the butt point  51  by a gear charge ratio G r  and for outputting a torque value T 2  after gear change, a multiplier  53  for multiplying the torque value T 2  after gear change by a differential gear ratio G f  and for outputting a torque value T 3  through the differential gear, and a multiplier  54  for multiplying the torque value T 3  through the differential gear by reciprocal 1/R of a tire diameter R and outputting a driving force F vehicle  of a tire surface. 
     The rotation computation system  50  comprises a multiplier  56  for multiplying a target vehicle speed V vehicle  by a tire slip ratio k from a calculator  55 , which obtains the tire slip ratio k, and for outputting the target vehicle speed V tar  after correction of slip ratio, a multiplier  57  for multiplying the target vehicle speed V tar  by a multiplier (1/2πR) concerning the tire diameter and for outputting a rotation angle speed n 1  of the tire, a multiplier  58  for multiplying the rotation angle speed n 1  of the tire by a multiplier (1/G f ) concerning the gear ratio and for obtaining a rotation angle speed n 2  closer to an entrance of the differential gear (closer to the engine), and a multiplier  59  for multiplying the rotation angle speed n 2  closer to the entrance of the differential gear by a multiplier (1/G r ) concerning the gear change ratio and for obtaining an engine rotation angle speed n 3  (corresponding to the V r ). 
     Reference numeral  60  represents a differentiator for differentiating the engine rotation angle speed n 3  and for outputting an engine rotation acceleration ω e  and reference numeral  61  represents a multiplier for multiplying the engine rotation acceleration ω e  by an engine inertia moment J e  and for outputting a torque value T e  caused by engine inertia. The torque value T e  caused by engine inertia is outputted to a butt point  51  of the torque computation system  49 . 
     In the above-described conventional engine testing apparatus, a single transmission efficiency constant, which concerns a transmission of engine output to a road surface and a driving force which accelerates the vehicle, is utilized. That is the transmission efficiency constant matches the rotation number of a roller for 2-shaft chassis dynamo with the rotation number of an actual vehicle where constant speed (normal) driving is presumed. 
     However, tire slippage occurs on the road surface under actual operating conditions (actual running vehicle in actual case). That is, in the conventional engine testing apparatus, as markedly shown in the 2-shaft chassis dynamo, it is impossible to reproduce the change of the slip ratio between the tire and the roller related to the difference in the tire deformation degree of the tire at the time of constant speed running, acceleration running and deceleration running. 
     To sum up, slip is not simulated in the conventional engine testing apparatus shown in FIG.  6 . For simulation conducted by the conventional testing apparatus, a difference is generated between the engine rotation pattern  30  converted from the target vehicle speed pattern  12   b  and the engine rotation pattern  31  measured when the actual vehicle runs on a chassis dynamo. It can be found from FIG. 6 that the engine rotation pattern  30  is shifted lower than the engine rotation pattern  31  at the time of acceleration and shifted higher than the engine rotation pattern  31  at the time of deceleration. 
     In order to reproduce the engine rotation of the actual vehicle running, it is necessary to consider the slippage between the tire and road surface in addition to the tire diameter, the final-drive ratio, the gear ratio and the vehicle inertia weight. However, in the case of the conventional engine testing apparatus, this point is lacking and therefore, an accurate simulation can not be conducted. 
     A first invention has been accomplished in view of the above circumstances, and an object of the first invention is to provide an engine testing apparatus capable of accurately conducting a simulation of a vehicle. 
     In the above-described conventional engine testing apparatus, as shown in FIGS. 5 and 9, the rotational acceleration of the engine  1  under test obtained in the rotation computation system  50  is multiplied by an inertia moment of the engine  1  under test, and the result is used in the torque computation in the torque computation system  49  to calculate a load. That is, the simulation is conducted such that at the time of acceleration, the output torque T E  corresponding to the inertia of the engine  1  under test is absorbed by the dynamometer  2 , and at the time of deceleration, the torque is increased on the contrary. 
     However, in the actual vehicle running in the actual case, inertia of other rotating bodies such as the transmission, a differential gear and a tire exert an influence upon the load, and in the case of the conventional engine testing apparatus, this consideration is lacking and thus, an accurate simulation can not be conducted. 
     A second invention has been accomplished in view of the above-described circumstances, and an object of the second invention is provide an engine testing apparatus capable of accurately conducting a simulation of a vehicle. 
     Since a rotational driving force of the engine through the transmission and differential gear is transmitted to the tire at a ratio of 1:1, it is conceivable that controlling the actual rotation number R a  of the dynamometer  2  is the same as controlling the rotation number of the engine in effect. From this point of view, in the engine testing apparatus, it is necessary to reproduce the rotation number of the engine in the actual running vehicle. 
     However, in the actual running vehicle in the actual case, tire slippage occurs on the road surface. The conventional engine testing apparatus does not take this slippage into consideration, i.e., tire slippage is not simulated. Thus, as shown in FIG. 6, in a simulation carried out in the conventional engine testing apparatus, a difference is generated between the engine rotation pattern  30  converted from the target vehicle speed pattern  12   b  and the engine rotation pattern  31  measured when the actual vehicle runs on a chassis dynamo. It can be found from FIG. 6 that the engine rotation pattern  30  is shifted lower than the engine rotation pattern  31  at the time of acceleration and shifted higher than the engine rotation pattern  31  at the time of deceleration. 
     To sum up, in order to reproduce the engine rotation of the actual running vehicle, it is necessary to take into consideration tire slippage between the tire and road surface in addition to the tire diameter, the final-drive ratio, the gear ratio, the vehicle inertia weight and the running resistance. However, in the case of the conventional engine testing apparatus, this point is lacking and therefore, an accurate simulation can not be conducted. 
     A third invention has been accomplished in view of the above circumstances, and an object of the third invention is to provide an engine testing apparatus capable of accurately conducting a simulation of a vehicle. 
     SUMMARY OF THE INVENTION 
     To achieve the above object, according to the first invention, there is provided an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test for simulating an actual vehicle running on a chassis dynamo, a dynamo controller for controlling rotation of the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test. The dynamo controller and the actuator are controlled to adjust an output of the engine under test, wherein a constant speed driving slip ratio (S a ) in a constant speed running state for a target vehicle speed pattern, an acceleration driving slip ratio (S b ) in an acceleration running state, and a deceleration driving slip ratio (S c ) in a deceleration running state are previously computed and stored as data for correcting tire slippage during the actual vehicle running. An engine target rotation number (R r ), which is obtained by converting the target vehicle speed pattern by values of the driving slip ratios (S a ), (S b ) and (S c ), is corrected for each of the running states. A new engine target rotation number obtained by this correction is used at the time of simulation, thereby controlling the rotation of the dynamometer. 
     According to another aspect of the first invention, there is provided an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test to simulate an actual vehicle running on a chassis dynamo, a dynamo controller for controlling rotation of the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test. The dynamo controller and the actuator are controlled to adjust an output of the engine under test, wherein a constant speed driving slip ratio (S a ) in a constant speed running state in a target vehicle speed pattern, an acceleration driving slip ratio (S b ) in an acceleration running state, and a deceleration driving slip ratio (S c ) in a deceleration running state are previously computed and stored as data for correcting tire slippage of the actual running vehicle. In each of the running states, the rotation number (R ta ) {[R ta =R r X(1+S a )], (R tb ) [R tb =R r X(1+S b )] or (R tc ) [R tc =R r X(1+S c )]}, which is obtained by adding to the engine target rotation number (R r ) a term obtained by multiplying the engine target rotation number (R r ) by the constant speed driving slip ratio (S a ), the acceleration driving slip ratio (S b ) or the deceleration driving slip ratio (S c ) is determined as a new rotation number subjected to a tire slip correction, and are used at the time of simulation, thereby controlling the rotation of the dynamometer. 
     The engine rotation pattern, which is obtained by converting from the target vehicle speed pattern in the conventional simulation, is shifted lower and higher than the engine rotation pattern of an actual vehicle running on a chassis dynamo. The present inventors have contemplated that this observation may be related to tire slippage. From this view point, a concept of introducing the driving slip ratio S was developed. The present inventors defined the driving slip ratio S using the average value of ratio between the engine rotation number shown by the engine rotation pattern and the engine rotation number shown by the engine rotation pattern. Further, since the engine rotation patterns are obtained from, for example, the target vehicle speed patterns including a constant speed (normal) section, an acceleration section and a deceleration section, each of states of constant speed, acceleration and deceleration can not be covered with one driving slip ratio S. From this point of view, the present inventors divided the driving slip ratio S into three kinds, i.e., constant speed, acceleration and deceleration, and respective slip ratios S a , S b  and S ca  were calculated. 
     The acceleration driving slip ratio S b  can be obtained in the following manner. 
     (1) Areas under acceleration curves A 1  to A 8  of the engine rotation pattern are obtained. For example, the area under the acceleration curve A 1  is G 1 ). These areas G 1  to G 8  are added. That is, G 1 + . . . +G 8  is determined as G. 
     (2) Areas under acceleration curves B 1  to B 8  in the engine rotation pattern are obtained. For example, the area under the acceleration curve B 1  is R 8  (shaded portion). These areas R 1  to R 8  are added. That is, R 1 + . . . +R 8  is determined as R. 
     Similar computations are conducted for all the deceleration curves C in the engine rotation pattern and all the deceleration curves D in the engine rotation pattern, thereby obtaining the slip ratio S c . 
     The constant speed slip ratio S a  can be obtained by carrying out similar computations. 
     After the data is obtained to correct for tire slippage of an actual vehicle, the present inventors added, to the engine target rotation number (R r ), a term obtained by multiplying the engine target rotation number (R r ) by the constant speed driving slip ratio S a , the acceleration driving slip ratio S b  or the deceleration driving slip ratio S c . The result was determined as a new rotation number R ta , R tb  or R tc  after tire slippage is corrected for each of the constant speed section, the acceleration section and the deceleration section. 
     In the engine testing apparatus of the above structure, in addition to the tire diameter, the final-drive ratio, the gear ratio, the vehicle inertia weight and the running resistance which are taken into consideration in the conventional engine testing apparatus, the slippage between the tire and the road surface is also taken into consideration and therefore, it is possible to accurately reproduce the engine rotation during actual vehicle running. 
     The engine rotation pattern, which is converted from the new rotation numbers R ta , R tb  or R tc  and which correct for tire slippage, is not shifted from the measured engine rotation pattern. The engine testing apparatus of the present invention in which the control computer controls the rotation of the dynamometer in accordance with the engine rotation pattern converted from the new rotation numbers R ta , R tb  or R tc , which correct for tire slippage, can carry out a simulation with high accuracy as compared with the conventional engine testing apparatus in which the control computer controls the rotation of the dynamometer in accordance with the engine rotation pattern converted from the target rotation number R r . 
     Further, to achieve the above object, according to the second invention, there is provided an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test, a dynamo controller for controlling the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test, the dynamo controller and the actuator are controlled to adjust an output of the engine under test, wherein rotational acceleration of rotating bodies such as the engine, a transmission, a differential gear and a tire are obtained based on the target vehicle speed pattern. Each of the rotational accelerations are multiplied by an inertia moment of each of the rotation bodies to calculate a torque absorbed by each of the rotating bodies, and the engine under test is controlled such that the engine under test outputs a predetermined torque while taking these absorbed torque. 
     In the engine testing apparatus of the above structure, in addition to the inertia moment of the engine which is taken into consideration in the conventional engine testing apparatus, the inertia moment of other rotating bodies such as the transmission, the differential gear and the tire are also taken into consideration and therefore, it is possible to accurately reproduce the engine load during actual vehicle running, and to carry out a simulation with high accuracy. 
     To achieve the above object, according to the third invention, there is, provided an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test to simulate an actual vehicle running on a chassis dynamo, a dynamo controller for controlling rotation of the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test A driving slip ratio (y) is computed and stored as a multiple-degree equation function y=f(T ff ) using, as a variable, an output torque (T ff ) output from a torque generator and required by the engine. The engine target rotation number (R r ) is corrected using this value, and the rotation of the dynamometer is controlled using this corrected new rotation number. 
     According to another aspect of the third invention, there is provided an engine testing apparatus comprising a dynamometer connected to an output section of an engine under test to simulate an actual vehicle running on a chassis dynamo, a dynamo controller for controlling rotation of the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test. Wherein a driving slip ratio (y) is computed as a multiple-degree equation function y=f(T ff ) using, as a variable, an output torque (T ff ) output from a torque generator and required by the engine, the rotation number (R t ) [R t =R r  X(1+y)] obtained by adding, to the engine target rotation number (R r ), a term obtained by multiplying the engine target rotation number (R r ) by the driving slip ratio (y) is determined as a new rotation number after the tire slip correction is made, and the rotation of the dynamometer is controlled by using this new rotation number. 
     The present inventors considered that the reason why the engine rotation pattern obtained by converting from the target vehicle speed pattern in the conventional simulation is shifted lower and higher than the engine rotation pattern measured on a chassis dynamo is related to tire slippage. From this view point, a concept of the rotation correcting ratio during the actual vehicle running, such as, the driving slip ratio (y), was introduced. This is because it is defined that the driving slip ratio (y) during the actual vehicle running is determined as function of acceleration of the vehicle, and the acceleration of this vehicle can be simulated by converting into the output torque of the engine. That is, this is because the torque supplied to the tire from the engine through the transmission and the differential gear is transmitted to the road surface and becomes a driving force which accelerates the vehicle. 
     Thereupon, the tire slip ratio (y) is defined by the multiple degree function y=f(T ff ) using the torque T ff  for achieving the target output from the torque generator as variable. 
     The present inventors multiplied the engine target rotation number R f  (simply target rotation number, hereinafter) output from the rotation generator in the simulation by the driving slip ratio (y). The obtained tire slip correction term (R r  X y) is added to the target rotation number R r , thereby making a new rotation number R t  which is corrected for the tire slippage. 
     In the engine testing apparatus of the above structure, in addition to the tire diameter, the final-drive ratio, the gear ratio, the vehicle inertia weight and the running resistance which are taken into consideration in the conventional engine testing apparatus, the slip between the tire and the road surface is also taken into consideration and therefore, it is possible to accurately reproduce the engine rotation of actual running vehicle. 
     As shown in FIG. 2, the engine rotation pattern  40 , which is converted from the new rotation number R t  which is corrected for tire slippage, is not shifted from the measured engine rotation pattern, the engine testing apparatus of the present invention in which the control computer controls the rotation of the dynamometer in accordance with the engine rotation pattern converted from the new rotation number R t  which is corrected for tire slippage, can carry out a simulation with high accuracy as compared with the conventional engine testing apparatus in which the control computer controls the rotation of the dynamometer in accordance with the engine rotation pattern converted from the target rotation number R r . 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows one example of a control flow in an engine testing apparatus according to a first invention; 
     FIG. 2 shows in comparing manner, an engine rotation pattern converted from a target vehicle speed pattern in a simulation carried out by the engine testing apparatus of the first and third inventions and an engine rotation pattern measured when an actual vehicle is allowed to run on a chassis dynamo; 
     FIG. 3 schematically shows the entire structure of the engine testing apparatus of the first, second and third inventions; 
     FIG.  4 (A) shows one example of the target vehicle speed pattern. 
     FIG.  4 (B) shows one example of the rotation target pattern. 
     FIG. 5 shows a control flow in a conventional engine testing apparatus; 
     FIG. 6 shows in comparing manner, an engine rotation pattern converted from a target vehicle speed pattern in a simulation carried out by the conventional engine testing apparatus and an engine rotation pattern measured when an actual vehicle is allowed to run on a chassis dynamo; 
     FIG. 7 shows one example of a control flow in the engine testing apparatus according to the second invention; 
     FIG. 8 shows one example of a computation flow in the engine testing apparatus according to the second invention; 
     FIG. 9 shows a computation flow in the conventional engine testing apparatus; and 
     FIG. 10 shows one example of a control flow in the engine testing apparatus according to the third invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of a first invention is explained with reference to the drawings. FIG. 1 shows one embodiment of the invention and shows a control flow in an engine testing apparatus shown in FIG.  3 . In comparison, FIG. 2 shows, an engine rotation pattern  40  converted from a target vehicle speed pattern  12   b  from a simulation carried out by the engine testing apparatus of the first invention and an engine rotation pattern  31  measured when an actual vehicle is allowed to run on a chassis dynamo. In FIGS. 1 and 2, members and elements represented with the same numerals as those in FIGS. 5 and 6 are the same and thus, explanations thereof will be omitted. 
     As shown in FIG. 1, the control flow of the engine testing apparatus of the first invention substantially differs from FIG. 5 of the above-described conventional engine testing apparatus, wherein a new rotation number which corrects for tire slippage is divided into a constant speed section, an acceleration section and a deceleration section, and using them, a dynamometer  2  is controlled. 
     This will be described in greater detail using the control flow shown in FIG.  1 . In FIG. 1, reference numeral  41  represents a driving slip correcting means provided between a rotation generator  16  and a delay correcting means  17 . 
     This driving slip correcting means  41  has a computation function for adding all areas under acceleration curves A 1  to A 8  in engine rotation patterns  31  shown in FIG. 6 
     {circle around ( 1 )}A computation function for adding all areas under acceleration curves B 1  to B 8  in engine rotation patterns  30  shown in FIG. 6, a function for computing a ratio (=acceleration driving slip ratio S b ) of each of total areas G and R obtained by the addition, a computation function for adding all areas under deceleration curves C in the engine rotation pattern  31  shown in FIG.  6 . 
     {circle around ( 2 )}A computation function for adding all areas under deceleration curves D in the engine rotation pattern  30  shown in FIG. 6, a function for computing a ratio (=deceleration driving slip ratio S c ) of each of total areas obtained by the addition, a computation function for adding all areas under constant speed curves E in the engine rotation pattern  31  shown in FIG.  6 . 
     {circle around ( 3 )}, A computation function for adding all areas under constant speed curves F in the engine rotation pattern  30  shown in FIG. 6, a function for computing a ratio (=constant speed slip ratio S a ) of each of total areas obtained by the addition, and further, 
     {circle around ( 4 )} a function for adding a term obtained by multiplying the engine target rotation number R r  by the acceleration driving slip ratio S b  to the target rotation number R r  to compute a new rotation number R tb  which is corrected for tire slippage, i.e., at the acceleration section, a function for computing the new rotation number R tb  for controlling the rotation of the dynamometer  2  according to the following equation (1): 
     
       
           R   tb   =R   r   X (1 +S   b )  (1) 
       
     
     {circle around ( 5 )} a function for adding a term obtained by multiplying the engine target rotation number R r  by the deceleration driving slip ratio S c  to the target rotation number R r  to compute a new rotation number R tc  which is corrected for tire slippage, i.e., at the deceleration section, a function for computing the new rotation number R tc  for controlling the rotation of the dynamometer  2  according to the following equation (2): 
     
       
           R   tc   =R   r   X (1 +S   c )  (2) 
       
     
     {circle around ( 6 )} a function for adding a term obtained by multiplying the engine target rotation number R r  by the constant speed driving slip ratio S a  to the target rotation number R r  to compute a new rotation number R ta  which is corrected for tire slippage, i.e., at the constant speed section, a function for computing the new rotation number R ta  for controlling the rotation of the dynamometer  2  according to the following equation (3): 
     
       
           R   ta   =R   r   X (1 +S   a )  (3) 
       
     
     For the control flow shown in FIG. 1, the driving slip correcting means  41  is provided between the rotation generator  16  and the delay correcting means  17 . From the driving slip correcting means  41 , the new target rotation number R tb  in which the driving slippage correction (tire slippage correction) is taken into consideration can be obtained at the time of acceleration, the new target rotation number R tc  in which the driving slip correction is taken into consideration can be obtained at the time of deceleration, and the new target rotation number R ta  in which the driving slip correction is taken into consideration can be obtained at the time of constant speed running. 
     By controlling the rotation of the dynamometer  2  in accordance with the new target rotation pattern represented by the above equation (1), it is possible to accurately reproduce the engine rotation of a vehicle during use in which slippage between the tire and the road surface at the time of acceleration running is taken into consideration. 
     By controlling the rotation of the dynamometer  2  in accordance with the new target rotation pattern represented by the above equation (2), it is possible to accurately reproduce the engine rotation of an actual running vehicle which slippage between the tire and the road surface at the time of deceleration running is taken into consideration. 
     Further, by controlling the rotation of the dynamometer  2  in accordance with the new target rotation pattern represented by the above equation (3), it is possible to accurately reproduce the engine rotation during actual vehicle running in which the slippage between the tire and the road surface at the time of constant speed running is taken into consideration. 
     As explained above, according to the engine testing apparatus of the first invention, a new target rotation pattern is made for each of the constant speed section, the acceleration section and the deceleration section while taking the slip between the tire and the road surface into consideration, and the rotation of the dynamometer is controlled in accordance with the new target rotation pattern. Therefore, it is possible to accurately simulate the operation of an actual vehicle, and to test the performance of the engine in a state close to the actual state of operation. 
     An embodiment of a second invention is explained with reference to the drawings. FIGS. 7 and 8 show one embodiment of the second invention, and show one example of a control flow and a computation flow in the engine testing apparatus shown in FIG.  3 . In FIGS. 7 and 8, members and elements represented with the same numerals as those in FIGS. 3,  5  and  9  are the same and thus, explanations thereof will be omitted. 
     As shown in FIG. 7, the control flow of the engine testing apparatus of the second invention substantially differs from the control flow of the above-described conventional engine testing apparatus show in FIG. 5, wherein a rotation control system  14  is provided, the circuit  62  for differentiating an output V r  of the rotation generator  16  is provided on a branch branching at a point  71  between the rotation generator  16  and the delay correcting circuit  17 , and a multiplier  63  for multiplying the output of the differentiator  62  by inertia moments of rotating bodies such as an engine, a transmission, a differential gear and a tire is provided in the rear stage of a differentiator  62  on this branch. The output from the multiplier  63  is added to an output T ff  of the torque generator  20  of the simulation vehicle control system  15  at an addition point  64 , and its added output is added to an output T fb  of the speed feedback controller  22 , and the result is determined as a control target torque T ctl . 
     This is explained in greater detail using a computation flow shown in FIG.  8 . In FIG. 8, the reference numerals  65 ,  66  and  67  represent differentiators. That is, the differentiator  65  differentiates the engine rotation angle speed n 3  output from the multiplier  59  to output a transmission rotation acceleration ω r . The differentiator  66  differentiates a rotation angle speed n 2  closer to an entrance of the differential gear output from the multiplier  58  to output a differential gear rotation acceleration ω f . The differentiator  67  differentiates a rotation angle speed n 1  of the tire to output a tire rotation acceleration ω w . 
     Multipliers  68 ,  69  and  70  for multiplying outputs from the differentiators  65 ,  66  and  67  by the predetermined multiplier are provided closer to output side of these differentiators  65 ,  66  and  67 . That is, the multiplier  68  multiples the transmission rotation acceleration ω r  by a transmission inertia moment J r , and outputs a torque T r  absorbed by the transmission to a butt point  71  provided immediately in front of the multiplier  52  of the torque computation system  49 . The multiplier  69  multiplies the differential gear rotation acceleration ω f  by a differential gear inertia moment J r , and outputs a torque T f  absorbed by the differential gear to a butt point  72  provided immediately in front of the multiplier  53  of the torque computation system  49 . The multiplier  70  multiplies the tire rotation acceleration ω w  by a tire inertia moment J w , and outputs a torque T w  absorbed by the tire to a butt point  73  provided immediately in front of the multiplier  54  of the torque computation system  49 . 
     In the engine testing apparatus of the above structure, as shown in the flowchart of FIG. 8, at a butt point  51 , an actual torque. T a  of the engine  1  under test is butted against a torque value T E  resulting from the inertia moment of the engine  1  under test. A torque value T 1  (=T a −T E ) is outputted from the butt point  51 . In the butt point  71 , the torque value T 1  is butted against a torque value T r  resulting from inertial moment of the transmission, and a torque value T 1 ′ (=T 1 −T t ) is outputted from the butt point  71 . The torque value T 1 ′ is multiplied by a gear change ratio G r  in the multiplier  52 , and a torque value T 2  is output. 
     At the butt point  72 , the torque value T 2  is butted against a torque value T f  resulting from differential gear, and a torque value T 2 ′ (=T 2 −T f ) is outputted from the butt point  72 . The torque value T 2 ′ is multiplied by a differential gear ratio G f  in the multiplier  53 , and a torque value T 3  is outputted. Further, at the butt point  73 , the torque value T 3  is butted against a torque value T w  resulting from the tire, and a torque value T 3 ′ (=T 3 −T w ) is outputted from the butt point  73 . The torque value T 3 ′ is multiplied by a multiplier (1/R) concerning the tire diameter R in the multiplier  54 , and a driving force F vehicle  at the tire surface is obtained. 
     As described above, in the engine testing apparatus of the above embodiment, in addition to the inertia moment of the engine which is taken into consideration in the conventional engine testing apparatus, torque resulting from the inertia moment of other rotating bodies such as the transmission, the differential gear and the tire are also computed. The torque is taken into consideration such that the engine under test outputs the predetermined torque and therefore, it is us possible to accurately reproduce the engine load during actual vehicle running and to carry out a simulation with high accuracy. 
     Although tire slippage is not taken into consideration in the above embodiment, it may be taken into consideration. In this case, in the control flow shown in FIG. 7, a tire slippage correcting circuit may be provided between the point  71  and the delay correcting circuit  17 , and an output T ff  of the torque generator  20  may be inputted to the tire slip correcting circuit. In this case, the simulation can be carried out with higher accuracy. 
     As explained above, according to the engine testing apparatus of the second invention, since the output of the engine under test is controlled while taking the inertia moment of each of rotating bodies such as the engine into consideration, it is possible to accurately simulate the running of an actual vehicle and to test the performance of the engine in a state close to the actual state. 
     An embodiment of a third invention is explained with reference to the drawings. FIG. 10 shows one embodiment of the third invention and shows one example of a control flow in the engine testing apparatus shown in FIG.  3 . By comparison, FIG. 2 shows, the engine rotation pattern  40 , which, is converted from the target vehicle speed pattern  12   b  in a simulation carried out by the engine testing apparatus of the third invention and the engine rotation pattern  31  measured when the actual vehicle is allowed to run on the chassis dynamo. In FIGS. 10 and 2, members and elements represented with the same numerals as those in FIGS. 5 and 6 are the same and thus, explanations thereof will be omitted. 
     Referring to FIG. 10 the control flow of the engine testing apparatus of the third invention substantially differs from the control flow of the above-described conventional engine testing apparatus of FIG. 5 in that the dynamometer  2  is controlled using a new rotation number R r  which is corrected for tire slippage. 
     This is explained in more detail using a control flow shown in FIG. 10 . In FIG. 10, the reference numeral  41  represents tire slippage correcting means provided between a rotation generator  16  and the delay correcting means  17 . 
     The tire slippage correcting means  41  has a function for computing a driving slip ratio (y) from the torque T ff  using multiple-degree equation function y=f(T ff ), a computation function for multiplying the target rotation number R r  output from the rotation generator  16  by the driving slip ratio (y), and a function for adding the obtained tire slippage correcting term (R r  X y) to the target rotation number R r  to compute a new rotation number R t  for controlling the rotation of the dynamometer  2  according to the following equation (1): 
     
       
           R   t   =R   r   X (1 +y )  (1) 
       
     
     That is, the driving slip ratio (y) is defined as a multiple-degree equation function y=f(T ff ) using the outputted torque (T ff ) output from the torque generator  20  and required by the engine. The torque (T ff ) is formed into a pattern as a known value. Thus, the driving slip ratio (y) can also be formed into a pattern. 
     Further, the target rotation number R r  of the dynamometer  2  is also formed into a pattern as a known value, the tire slip correcting term (R r  X y) can by obtained by multiplying the target rotation number R r  by the driving slip ratio (y). 
     For example, the following equations (2) and (3) can be employed as the multiple-degree equation function y=f (T ff ): 
     (i) when y is closer to a first degree equation, 
     
       
           y=f ( T   ff )= AXT   ff   +B   (2) 
       
     
     (ii) when y is closer to a second degree equation, 
     
       
           Y=f ( T   ff )= A (( T   ff ) 2   +BXT   ff   +C   (3) 
       
     
     (wherein A, B and C are constants). 
     In case (i), it is possible to accurately reproduce the engine rotation number of the actual running vehicle in which slippage between the tire and the road surface is taken into consideration by controlling the rotation of the dynamometer  2  in accordance with a new target rotation pattern represented by the following equation (4): 
     
       
           R   t   =R   r   X [1+( AXT   ff   +B )]  (4) 
       
     
     by substituting equation (2) into equation (1). 
     In the case of the (ii), the rotation of the dynamometer  2  is controlled in accordance with a new target rotation pattern represented by the following equation (5): 
     
       
           R   t   =R   r   X [1+( A ( T   ff ) 2   +BXT   ff   +C )]  (5) 
       
     
     by substituting equation (3) into equation (1). 
     In this manner, in the control flow shown in FIG. 10, the tire slippage correcting means  41  is provided between the point  81  and the delay correcting circuit  17 , the output T ff  of the torque generator  20  is inputted to the tire slippage correcting means  41 , and the new target rotation number R r  in which the tire slippage correction is taken into consideration can be obtained, and the rotation of the dynamometer  2  is controlled in accordance with the target rotation number R t  Therefore, it is possible to accurately reproduce the engine load during actual vehicle running and to carry out a simulation with high accuracy. 
     As explained above, according to the engine testing apparatus of the third invention, a new target rotation pattern is made while taking slippage between the tire and the road surface into consideration, and the rotation of the dynamometer is controlled in accordance with the new target rotation pattern. Therefore, it is possible to accurately simulate the actual running vehicle, and to test the performance of the engine in a state close to the actual state during operation.