Land Rover Diesel Distributor Pumps Bosch Bosch Manual
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Advantages – Flexible adaptation enables optimi- zation of engine behavior and emission control. – Clear-cut delineation of individual func- tions: The curve of full-load injected fuel quantity is independent of governor characteristic and hydraulic configuration. – Processing of parameters which pre- viously could not be performed me- chanically (e.g., temperature-correction of the injected fuel quantity characteris- tic, load-independent idle control). – High degree of accuracy throughout complete service life due to closed con- trol loops which reduce the effects of tolerances. – Improved driveability: Map storage enables ideal control characteristics and control parameters to be established independent of hydraulic effects. These are then precisely adjusted during the optimisation of the complete engine/ vehicle system. Bucking and idle shake no longer occur. – Interlinking with other electronic sys- tems in the vehicle leads the way towards making the vehicle safer, more comfortable, and more economical, as well as increasing its level of environ- mental compatibility (e.g., glow systems or electronic transmission-shift control). The fact that mechanical add-on units no longer need to be accomodated, leads to marked reductions in the amount of space required for the fuel-injection pump. Engine shutoff As already stated on Page 40, the prin- ciple of auto-ignition as applied to the diesel engine means that the engine can only be switched off by interrupting its supply of fuel. When equipped with Electronic Diesel Control (EDC), the engine is switched off by the injected-fuel quantity actuator (Input from the ECU: Injected fuel quantity = Zero). As already dealt with, the separate electrical engine shutoff device serves as a standby shutoff in case the actuator should fail. Electrical shutoff device The electrical shutoff device is operated with the “ignition key” and is above all used to provide the driver with a higher level of sophistication and comfort. On the distributor fuel-injection pump, the solenoid valve for interrupting the supply of fuel is fitted in the top of the distributor head. With the diesel engine running, the inlet opening to the high- pressure chamber is held open by the en- ergized solenoid valve (the armature with sealing cone is pulled in). When the “igni- tion switch” is turned to “Off ”, the power supply to the solenoid is interrupted and the solenoid de-energized. The spring can now push the armature with sealing cone onto the valve seat and close off the inlet opening to the high-pressure cham- ber so that the distributor plunger can no longer deliver fuel. Electronic control for distributor pumps 59 Failure Monitoring Reaction Warning Diagnostic of lamp output Correction Signal range Reduce injected l sensors fuel quantity System- Signal range Limp-home sensors or emergencyll function (graded) Computer Program runtime Limp-home (self-test) or emergencyll function Fuel-quantity Permanent Engine shutoff ll actuator deviation Table 1. ECU reactions
Prospects On the electronically-controlled distrib- utor pumps of the future, the electrical actuator mechanism with control collar for fuel metering will be superseded by a high-pressure solenoid valve. This will permit an even higher degree of flexibility in the fuel metering and in the variability of the start of injection. Design and construction This pump is of modular design. The field- proven distributor injection pump can thus be combined with a new electronically controlled fuel-metering system (Fig. 1). Basically speaking, the solenoid-valve- controlled distributor pump’s dimensions, installation conditions, and drivetrain in- cluding the pump’s cam drive, are identi- cal to those of the conventional distributor pump. The most important new compo- nents are: – Angle-of-rotation sensor (in the form of an incremental angle/time system [ IWZ] ) which is located in the injection pump on the driveshaft between the vane-type supply pump and the roller ring, – Electronic pump ECU, which is mount- ed as a compact unit on the top side of the pump and connected to the engine ECU, – High-pressure solenoid valve, installed in the center of the distributor head. With regard to its installation and hydrau- lic control, the timing device with pulse valve is identical to the one in the pre- vious electronically-controlled distributor pump. Components Angle-of-rotation sensor Angle-of-rotation detection uses the following components: Sensor, sensor retaining ring on the driveshaft, and the trigger wheel with a given tooth pitch. Detection is based upon the signals generated by the sensor. The pulses generated by the sensor are inputted to the ECU where they are pro- cessed by an evaluation circuit. The fact that the sensor is coupled to the pump’s roller ring ensures the correct assign- ment of the angular increment to the position of the cam when the roller ring is rotated by the timing device. Pump ECU The pump ECU is mounted on the upper side of the pump and uses hybrid tech- niques. In addition to the mechanical loading with which it is confronted in the vehicles under-hood environment, the pump must also fulfill the following assignments: – Data exchange with the separately mounted engine ECU via the serial bus system, – Evaluation of the signal from the angle-of-rotation sensor (IWZ), – Triggering of the high-pressure sol- enoid valve, – Triggering of the timing device. Maps are stored in the pump ECU which not only take into account the setting points for the particular vehicle applica- tion and certain engine characteristics, but also permit the plausibility of the re- ceived signals to be checked. In addition, they form the basis for defining a number of different computational values. Axial-piston distributor pumps, VE-MV 60 Solenoid-valve-controlled axial-piston distributor fuel-injection pumps VE-MV
High-pressure solenoid valve The high-pressure solenoid valve must fulfill the following assignments: – Large valve cross-section for efficient filling of the high-pressure chamber, even at very high rotational speeds, – Low weight (low moving masses), to keep the loading of the parts to a mini- mum, – Short switching times to guarantee high-precision fuel metering, and – Magnetic forces which are powerful enough to cope with the high pressures. The high-pressure solenoid valve is com- prised of: – The valve body, – The valve needle, and – The electromagnet with electrical connection to the pump ECU. The magnetic circuit is concentric to the valve. This fact permits a compact as- sembly comprising high-pressure sol- enoid valve and distributor head. Method of operation Principle Pressure generation in the solenoid- valve-controlled distributor injection pump is based on the same principle as that in the conventional electronically- controlled VE pump. Fuel supply and delivery Via the distributor head and the opened high-pressure solenoid valve, the vane- type supply pump delivers fuel to the high-pressure chamber at a pressure of approx. 12 bar. No fuel is delivered when the high-pres- sure solenoid valve is de-energized (open). The valve’s instant of closing defines the injection pump’s start of delivery. This can be located at the bottom dead center (BDC) of the cam or on the rise portion of the cam slope. Similarly, the valve’s instant of opening defines the pump’s end of delivery. The length of time the valve is closed deter- mines the injected fuel quantity. The high pressure generated in the high- pressure chamber (the fuel from the supply pump is compressed by the axial piston when this is forced up by the cam plate riding over the rollers of the roller ring) opens the delivery valve and the fuel is forced through the pressure line to the injection nozzle in the nozzle holder. Injection pressure at the nozzle is 1400 bar. Excess fuel is directed back to the tank through return lines. Since there are no additional intake ports available, if the high-pressure solenoid valve should fail, fuel injection stops. This prevents uncontrolled “racing” of the engine. Electronic control for distributor pumps 61 Solenoid-valve-controlled axial-piston distributor fuel-injection pump (section) Fig. 1 UMK1205Y
Since leakage and heat losses reduce the pressure and the temperature of the A/F mixture at the end of the compression stroke, the cold diesel engine is more diffi- cult to start and the mixture more difficult to ignitethan it is when hot. These facts make it particularly important that start-assist systemsare used. The minimum starting temperature depends upon the engine type. Pre-chamber and swirl-chamber engines are equipped with a sheathed- element glow plug (GSK) in the auxiliary combustion chamber which functions as a “hot spot”. On small direct-injection (DI) engines, this “hot spot” is located on the combustion chamber’s periphery. Large DI truck engines on the other hand have the alternative of using air preheating in the intake manifold (flame start) or special, easily ignitable fuel (Start Pilot) which is sprayed into the intake air. Today, the start- assist systems use sheathed-element glow plugs practically without exception. Sheathed-element glow plug The sheathed-element glow plug’s tubular heating element is so firmly pressed into the glow-plug shell that a gas-tight seal isformed. The element is a metal tube which is resistant to both corrosion and hot gases, and which contains a heater (glow) element embedded in magnesium-oxide powder (Fig. 1). This heater element comprises two series-connected resistors: the heater filament in the glow-tube tip, and the con- trol filament. Whereas the heater filament maintains virtually constant electrical resistance regardless of temperature, the control filament is made of material with a positive temperature coefficient (PTC). On newer-generation glow plugs (GSK2), its resistance increases even more rapidly with rising temperature than was the case with the conventional S-RSK glow plug. This means that the newer GSK2 glow plugs are characterized by reaching the temperature needed for ignition far more quickly (850 °C in 4s). They also feature a lower steady-state temperature (Fig. 2) which means that the glow plug’s tem- perature is limited to a non-critical level. The result is that the GSK2 glow plug can remain on for up to 3 minutes following engine start. This post-glow feature improves both the warm-up and run-up phases with considerable im- provements in noise and exhaust-gas emissions. Start-assist systems 62 Sheathed-element glow plug GSK2 1Electrical connector terminal, 2Insulating washer, 3Double gasket, 4Terminal pin, 5Glow-plug shell, 6Heater seal, 7Heater and control filament, 8Glow tube, 9Filling powder. 98 754 2316 UMS0685-1Y Start-assist systems Fig. 1
Flame glow plug The flame glow plug burns fuel to heat the intake air. Normally, the injection system’s supply pump delivers fuel to the flame plug through a solenoid valve. The flame plug’s connection fitting is pro- vided with a filter, and a metering device which permits passage of precisely the correct amount of fuel appropriate to the particular engine. This fuel then evaporates in an evaporator tube sur- rounding the tubular heating element and mixes with the intake air. The resulting mixture ignites on the 1,000 °C heating element at the flame-plug tip. Glow control unit For triggering the glow plugs, the glow control unit (GZS) is provided with a power relay and a number of electronic switching blocks. These, for instance, control the glow duration of the glow plugs, or have safety and monitoring functions. Using their diagnosis func- tions, more sophisticated glow control units are also able to recognise the failure of individual glow plugs and inform the driver accordingly. Multiple plugs are used as the control inputs to the ECU. In order to avoid voltage drops, the power supply to the glow plugs is through suitable threaded pins or plugs. Functional sequence The diesel engine’s glow plug and starter switch, which controls the preheat and starting sequence, functions in a similar manner to the ignition and starting switch on the spark-ignition (SI) engine. Switching to the “Ignition on” position starts the preheating process and the glow-plug indicator lamp lights up. This extinguishes to indicate that the glow plugs are hot enough for the engine to start, and cranking can begin. In the following starting phase, the drop- lets of injected fuel ignite in the hot, com- pressed air. The heat released as a result leads to the initiation of the combustion process (Fig. 3). In the warm-up phase following a suc- cessful start, post-heating contributes to faultless engine running (no misfiring) and therefore to practically smokeless engine run-up and idle. At the same time, when the engine is cold, pre- heating reduces combustion noise. A glow-plug safety switchoff prevents battery discharge in case the engine cannot be started. The glow-control unit can be coupled to the ECU of the Electronic Diesel Control (EDC) so that information available in the EDC control unit can be applied for optimum control of the glow plugs in accordance with the particular operating conditions. This is yet another possibility for reducing the levels of blue smoke and noise. Sheathed- element glow plugs, Flame glow plugs 63Sheathed-element glow plugs: Temperature-time diagram 1S-RSK, 2GSK2. Typical preheating sequence 1Glow-plug and starter switch, 2Starter, 3Glow-plug indicator lamp, 4Load switch, 5Glow plugs, 6Self-sustained engine operation, t vPre-heating time, tSReady to start, t NPost-heating time. tVtStN 1 2 3 4 5 6Time t 01020304050 650 750 850 950 1,050 1,150 s °C 1 2 Time t Temperature Fig. 2 UMS0688E Fig. 3 UMS0667-1E
(4.0) 1 987 722 164KH/PDI-04.99-En The ProgramOrder Number Gasoline-engine management Emission Control (for Gasoline Engines) 1 987 722 102 Gasoline Fuel-Injection System K-Jetronic 1 987 722 159 Gasoline Fuel-Injection System KE-Jetronic 1 987 722 101 Gasoline Fuel-Injection System L-Jetronic 1 987 722 160 Gasoline Fuel-Injection System Mono-Jetronic 1 987 722 105 Ignition 1 987 722 154 Spark Plugs 1 987 722 155 M-Motronic Engine Management 1 987 722 161 ME-Motronic Engine Management 1 987 722 178 Diesel-engine management Diesel Fuel-Injection: An Overview 1 987 722 104 Diesel Accumulator Fuel-Injection System Common Rail CR 1 987 722 175 Diesel Fuel-Injection Systems Unit Injector System / Unit Pump System 1 987 722 179 Radial-Piston Distributor Fuel-Injection Pumps Type VR 1 987 722 174 Diesel Distributor Fuel-Injection Pumps VE 1 987 722 164 Diesel In-Line Fuel-Injection Pumps PE 1 987 722 162 Governors for Diesel In-Line Fuel-Injection Pumps 1 987 722 163 Automotive electrics/Automotive electronics Alternators 1 987 722 156 Batteries 1 987 722 153 Starting Systems 1 987 722 170 Electrical Symbols and Circuit Diagrams 1 987 722 169 Lighting Technology 1 987 722 176 Safety, Comfort and Convenience Systems 1 987 722 150 Driving and road-safety systems Compressed-Air Systems for Commercial Vehicles (1): Systems and Schematic Diagrams 1 987 722 165 Compressed-Air Systems for Commercial Vehicles (2): Equipment 1 987 722 166 Brake Systems for Passenger Cars 1 987 722 103 ESP Electronic Stability Program 1 987 722 177 Automotive electric/electronic systemsSafety, Comfort and Convenience Systems Technical Instruction ¾® Automotive Electric/Electronic SystemsLighting Technology Technical Instruction ¾® Vehicle safety systems for passenger carsESP Electronic Stability Program Technical Instruction ¾® Engine management for diesel enginesRadial-Piston Distributor Fuel-injection Pumps Type VR Technical Instruction ¾® Electronic engine management for diesel enginesDiesel Acumulator Fuel-Injection System Common Rail Technical Instruction ¾® Engine management for spark-ignition enginesEmission Control Technical Instruction ¾® Gasoline-engine managementME-Motronic Engine Management Technical Instruction ¾® Engine management for spark-ignition enginesSpark Plugs Technical Instruction ¾® Brake systems for passenger carsBrake Systems Technical Instruction ¾®