FR2751410A1 - Testing internal combustion engines on production line - Google Patents

Abstract

Internal combustion engines for vehicles (M) pass along a production line (10) of work stations (P1,P2,P3.....) on trolleys (12). A test station (PT) is located immediately after the last work station (PN) and each engine is connected to electrical and fuel circuits and to the test equipment. It has been found that faults may be detected with virtually the same efficiency in a period of thirty seconds as over a much lengthier period by detailed analysis of parameters such as crankshaft rotation. In this short period the engine does not heat up appreciably and the connection of cooling equipment may be dispensed with further reducing the total time necessary.

Description

METHOD AND INSTALLATION FOR TESTING
INDIVIDUALLY COMBUSTION ENGINES
CHAIN PRODUCTS
The present invention relates to a method and an installation for individually testing combustion engines, intended in particular for equipping motor or road vehicles, which are assembled on a production line.

 The mass production of internal combustion engines is carried out by assembling the various components of the engine on a chain or production line formed of successive workstations on which the various operations are carried out, leading to the production of an engine which will then be sent to a line or assembly line of motor or road vehicles receiving the engines.

 The chain production of the motors makes it possible to ensure the assembly of each motor with extremely short production cycle times (duration of operations at each of the stations of the assembly line), generally less than or equal to approximately one minute. .

 Before shipping the assembled motors, it is necessary to test them individually and systematically in order to detect, before their assembly on the vehicles, malfunctions resulting from manufacturing defects and / or assembly of the components.

 These malfunctions or failures are, for example, leaks from the fuel supply and lubrication circuits of the engine.

 To this end, according to a known method, each engine is placed on a test bench on which the various test and / or measurement operations are carried out, when empty and / or loaded.

 A classic test cycle consists of placing the engine on the test bench, connecting the different engine circuits, then running the engine for a first warm-up period, performing test and measurement operations properly speaking during a period called "engine reception", then disconnecting the various circuits which connect the engine to the test bench.

 The engine is then evacuated from the test bench.

 According to known methods for individual engine testing, the overall duration of the steps for controlling an engine is between approximately 10 and 15 minutes.

 This duration is significantly greater than the average time of an engine production cycle and therefore requires increasing the number of test benches so as not to slow down the production rate. These test benches are conventionally fitted out in a sector or group of test benches at the end of the production chain and require complex systems for supplying motors from the assembly line and then grouping them together. below after their control.

 An example of such a particularly complex and costly arrangement is described and represented in document FR-A-2,683,803 which, in addition to the multiplication of the number of test benches, provides for means of handling and transfer of the engines.

 Another solution, just as expensive and complex, consists in using a test carousel as described and shown in document GB-A-2,225,163.

 Finally, the document FR-A-2,683,803 describes and represents another arrangement of a test sector fitted at the end of an engine assembly line and which comprises a multiplicity of test benches on which are carried out load tests with in particular different exhaust gas measurement operations for different engine operating regimes.

 The object of the present invention is to propose a method for individually testing the motors assembled on a production line which makes it possible to dispense with the layout of complex test installations.

To this end, the invention proposes a method for individually testing combustion engines which are assembled on a production line formed of successive work stations, this method comprising
- a step of setting up each engine on a test bench
a test step during which test and / or measurement operations are carried out on the engine; and
- an evacuation step for the tested engine.

According to the invention, the method is characterized in that the test step comprises the following operations
- start the engine
- control the motor according to a predefined operating cycle
- produce signals representative of the different combustions occurring in each of the engine cylinders during a predetermined observation period.

According to other characteristics of the process according to the invention
- the signals representative of the different combustions occurring in each of the engine cylinders during a predetermined observation period are subject during the test step, to digital processing to evaluate the stability of the combustions in each of the engine cylinders , stability from which the conformity of the engine is determined
- the signal representative of combustion occurring in an engine cylinder is deduced from the measurement of the instantaneous rotation speed of the crankshaft
- the duration of the test stage is less than 30 seconds
- the installation stage includes operations for connecting the electrical circuits and the engine fuel supply to associated circuits of the test bench, without connecting the cooling circuit of the engine to be tested
- the installation stage includes operations for connecting the engine exhaust circuit to an associated circuit of the test bench.

 The invention also provides an installation for the chain production of combustion engines of the type comprising successive work stations for the assembly and testing of each engine.

 According to the invention, this installation is characterized in that it comprises a test station which successively receives all the assembled motors, this test station cooperating with test and measurement means performing in particular the starting of the motor, the control of the engine according to a predetermined operating cycle, the measurement of the instantaneous rotation speed of the engine and the digital processing of these values.

 The post of. test includes means for connecting the electrical and fuel supply circuits of the engine to be tested and it does not include means for connecting the engine cooling circuit.

 Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawing, the single figures of which schematically illustrate an installation for the chain production of motors, carried out in accordance with the teachings of the invention.

 Figure 1 illustrates schematically and in top view a line or chain 10 of assembly in large series of motors M each of which is mounted and clamped on a carriage or conveyor plate 12 which travels along the chain, in the direction indicated by the arrows in the figure to pass successively in front of different work stations P1, P2 .... PN at each of which are carried out assembly and assembly operations of the various components of the engine.

 The PN station is the last assembly and assembly station for the M motors.

 The various stations of the chain 10 may also include intermediate test stations intended to control certain stages of assembly and assembly, and for example stations for testing the tightness of the various liquid circuits of the engine making it possible to control the quality tightness just after completion of the latter.

 In accordance with the teachings of the invention, the production line 10 comprises, arranged immediately after the last PN work station, a PT test station to which the motor M arrives, carried by its plate 12 and to which a test cycle will be carried out individual of each engine assembled in accordance with the method according to the invention.

The PT test station essentially comprises a test bench 14 with means 16, 18, 20, shown schematically in the figure, for connecting the motor
M to be tested on test bench 14 by ensuring the connection of the electrical circuit, the fuel supply circuit and possibly the engine exhaust circuit respectively.

 In accordance with the teachings of the invention, and given the very reduced overall duration of the steps for checking according to the invention of each engine, no means are provided for connecting the cooling circuit of the engine to be tested to a circuit. associated with the test bench 14.

 After setting up and connecting the engine M to the test bench 14, the actual test step is then carried out, during which tests and / or measurements are carried out on the engine. assembled and finished, aimed at detecting possible manufacturing defects and malfunctions.

 These operations carried out automatically by means of suitable means equipping the test bench 14, more precisely consist in starting the engine M, then in controlling the latter according to a predefined operating cycle for example so as to reach a rotation speed. stabilized setpoint and then measure certain engine operating parameters characteristic of the level of combustion in each of the engine cylinders such as the instantaneous speed of rotation of the crankshaft.

 Measuring the instantaneous speed of rotation of the crankshaft combined with a keying system makes it possible to produce signals representative of the gas torque produced by each of the different combustions occurring in each of the engine cylinders.

 The analysis of these signals by appropriate digital processing means then makes it possible to evaluate both the rotation speed actually reached by the engine and the stability and the level of combustion, cylinder by cylinder.

 These evaluations then make it possible to easily diagnose the various malfunctions resulting from manufacturing or assembly defects of the components, such as a high pressure fuel supply line disconnected or an incorrectly calibrated distribution, etc.

In accordance with the test and measurement operations described above, the presence of a malfunction involving the non-compliance of an engine, is determined by the occurrence of one of the following events
- the engine cannot be started within a predetermined period of time depending on the type of engine
- the engine having started, cannot reach the set speed within a predetermined period of time depending on the type of engine
- appearance of combustion instabilities in at least one cylinder, once the engine has reached its set speed.

 These various events are directly detected in real time and in a software manner by an electronic calculation unit operating the digital processing of the instantaneous crankshaft rotation speed information provided by an angular position sensor cooperating for example, with a toothed target integral with the crankshaft .

 The Applicant has been able to show that these various events not only make it possible to identify all of the malfunctions highlighted during test operations according to the known prior art but also make it possible to identify malfunctions hitherto ignored such as for example a nozzle partially closed injector that can be identified by the resulting loss of torque.

 The Applicant has also been able to show that the analysis of the instantaneous speed of the crankshaft, when the engine has reached its stabilized reference speed, can be carried out perfectly reliably over an observation period of less than 10 seconds.

 In accordance with the invention, the test and measurement operations are fully automated, which therefore makes it possible to carry out the control of the conformity of the motors without any operator intervention, thus guaranteeing greater precision and greater reliability in the results.

 Once the test step has been completed, the various connections 16 to 20 are disconnected and the engine tested is evacuated, for example to a storage unit (not shown) or to transfer means to a vehicle assembly unit. Engines declared non-compliant are automatically directed to touch-up stations.

 The actual test step is therefore carried out quickly with a very short duration. By choosing an appropriate operating cycle, the Applicant has found that it is possible to operate all of the test and measurement operations in less than 30 seconds.

 The effective operating time of the engine being reduced compared to the prior art, it is therefore not necessary to cool the engine, which therefore makes it possible to dispense with the connection of the engine to an external cooling circuit belonging to, test bench 14, which further reduces the duration of the test operations.

 Since the overall duration of a test cycle corresponding to the steps for checking an engine is less than the engine production cycle time, a single test bench 14 integrated into production line 10 is sufficient to individually test all the motors produced, without disturbing the flow of motors along line 10, and without requiring intermediate storage.

 In the schematic representation of the figure, the PT test station is illustrated perfectly in "line" with the workstations P1 to PN, but it is of course possible to arrange the single PT test station laterally or in diversion without leaving of the scope of the invention.

 The reduction in the duration of the test stage during which the engine operates also makes it possible to significantly reduce the pollution phenomena of the assembly plant and to reduce operating costs.

 Of course, the invention is in no way limited to the embodiment described and illustrated, which has been given only by way of example.

 On the contrary, the invention includes all the technical equivalents of the means described and their combinations if these are carried out according to the spirit.

 The test operations described can be carried out not only on a specific PT test station but also on any other Pi station in the manufacturing line 10 where this is possible such as the diesel fueling station in the case where the engines M are compression ignition engines.

 Indeed, the fuel injection pumps of diesel engines must be boosted on the production line 10 in a station where the engine is supplied with fuel and where the latter is rotated. It is therefore easy to integrate the test means provided at the PT station into this station.

 Likewise, the instantaneous speed of rotation of the crankshaft can be replaced by any other quantity capable of characterizing the level of combustion occurring in the various cylinders of the engine.

Claims (8)

 1. Method for individually testing combustion engines (M) which are assembled on a production line (10) formed of successive work stations (P1-PN), comprising  - a step of setting up each engine (M) on a test bench (14)  - a test step during which test and / or measurement operations are carried out on the engine (M); and  - a step of evacuating the tested engine, characterized in that the test step comprises the following operations  - start the engine (M)  - control the motor (M) according to a predefined operating cycle  - produce signals representative of the different combustions occurring in each of the engine cylinders (M) during a predetermined observation period.  2. Method according to claim 1, characterized in that said signals representative of the different combustions occurring in each of the engine cylinders (M) during a predetermined observation period are the subject during the test step, of a digital processing to assess the stability of combustion in each of the engine cylinders, stability from which the conformity of the engine is determined (M).  3. Method according to any one of the preceding claims, characterized in that said signal representative of combustion occurring in a cylinder of the engine (M) is deduced from the measurement of the instantaneous rotation speed of the crankshaft.  4. Method according to any one of the preceding claims, characterized in that the duration of the test step is less than 30 seconds.  5. Method according to any one of the preceding claims, characterized in that the positioning step comprises operations for connecting the electrical circuits and the fuel supply of the engine (M) to associated circuits (16, 18 ) of the test bench (14), without connection of the cooling circuit of the engine to be tested.  6. Method according to claim 5, characterized in that the installation step comprises operations for connecting the engine exhaust circuit to an associated circuit (20) of the test bench (14).  7. Installation for the chain production (10) of combustion engines (M) of the type comprising successive work stations (P1 PN, PT) for the assembly of components and the test of each motor (M), characterized in that it comprises a test station (PT) which successively receives all the assembled motors, this test station (PT) cooperating with test and measurement means performing in particular the starting of the engine, the control of the engine according to a predetermined operating cycle, the measurement of the instantaneous rotation speed of the engine and the digital processing of these values.  8. Installation according to claim 6, characterized in that the test station (PT) comprises means (16, 18) for connecting the electrical and fuel supply circuits of the engine (M) to be tested and does not include means for connecting the engine cooling circuit (M)