DK173135B1 - Hydraulic system for an internal combustion engine and with several of its shaft driven high pressure pumps. - Google Patents

Description

in DK 173135 B1

The invention relates to a hydraulic system for a combustion engine with multiple fuel pumps and multiple exhaust valves, wherein at least one high pressure pump supplies hydraulic drive devices, such as pump drives for the fuel pumps and hydraulic actuators for the exhaust valves, with energy from pressurized hydraulic fluid.

For many years, there have been separate proposals that the fuel pumps and exhaust valves of a large two-stroke cross-head motor should be hydraulically activated instead of the very well-known kamak cell activation. The applicant's Danish patent No. 41046 of 1929 proposed a hydraulic fuel pump, and from recent times Danish patent no.

151145 on a hydraulically operated fuel pump and Danish Patent No. 148,664 on an electronically controlled and hydraulically actuated exhaust valve.

The various known proposals for purely hydraulic actuation of exhaust valves and burning ice pumps on large two-stroke cross-head motors have not found simultaneous commercial use due to the complicated design of the hydraulic feed systems in combination with the large energy consumption that can help keep them hydraulic units equipped with high pressure hydraulic fluid. A prerequisite for commercial manufacture of an internal combustion engine without camshaft, i.e. without the mechanical actuation of fuel pumps and exhaust valves, the hydraulic drive devices have a hydraulic feed system that is reliable and energy efficiently designed. Furthermore, when the internal combustion engine is used as the main engine in a ship, operational safety is important.

It is characteristic of the drive devices' need for hydraulic fluid that they consume a greater amount per time when the engine load is greater. If the "35 high-pressure pump is designed to meet the unit's volume requirements at full engine load, excess capacity will be high at low load.

The invention has for its object to provide a hydraulic system that is both reliable and at the same time provides an advantageously low energy consumption.

To this end, the invention is characterized in that the hydraulic system comprises at least three high pressure pumps, at least two of which are primary pumps, which are shaft driven by the internal combustion engine, so that their rpm varies in a predetermined ratio with the speed of the engine crankshaft and at least one of which is a control pump. , which is electrically powered and has controllable delivery volume.

The breakdown of the delivery volume of at least three 15 pumps improves the overall reliability of the engine because the consequences of failure in one pump do not result in as much loss of delivery capacity as in only two pumps and do not lead to an operating condition where there is no spare pump. Safety is also substantially improved by the fact that at least two of the pumps are shaft-driven primary pumps, which may have substantially simpler in-house designs than an electrically driven control pump, and the direct coupling of a pump to a shaft is one of the most reliable pump drives, that is known.

The shaft connections of the primary pumps thus provide a safe supply of hydraulic fluid as the combustion engine shaft rotates.

In energy terms, several benefits are achieved. First, the division of the pumping work into more than 30 pumps better allows the individual pump to run close to its design point with optimum operating conditions, because each pump is exposed to less variation in delivery volume. Second, the delivery from the pumps can be switched on and off in finer stages when the number of 35 pumps is larger. Third, the transmission Λ · 3 DK 173135 B1 is advantageously low in the shaft connection of the primary pumps. Fourth, in the case of internal combustion engines that change speed at load changes, a partial adjustment of the supply quantity to the instantaneous load is achieved, because the primary pump also changes the speed and thus the supply quantity. These conditions provide an advantageous low energy consumption for the supply of high pressure hydraulic fluid. The electrically driven control pump provides a further possibility of fine-tuning the delivery amount to the instantaneous need for hydraulic fluid of the drive devices. Since the control pump is electrically powered, its supply quantity can be controlled completely independently of the combustion engine's operating condition.

15 The high reliability of the high-pressure pumps and their relatively low energy consumption allow the hydraulic system and associated drive devices to replace the traditional camshaft in large two-stroke cross-head engines, used inter alia as propulsion engines in ships.

According to the invention, it is possible to use primary pumps that are quantity adjustable in addition to the control due to their rpm, but it is preferred that each primary pump provides a constant supply quantity per shaft rotation. This provides an improvement in operational safety because the pumps can be designed with a few components, for example as standard displacement axial piston pumps of standard type.

Since at least some of the primary pumps do not need to be quantity adjustable at fixed rpm, they can be better optimized for the operating conditions and thus have substantially greater efficiency than the control pump which is quantity adjustable and more complicated in design.

35 For further optimization of the energy consumption \ 4 DK 173135 B1 it is preferred that the control pump is connected to an electric motor / generator unit and is controllable from a pump mode, where it is driven by the electric motor and supplies pressurized hydraulic fluid, to a motor-5 state where it consumes pressurized hydraulic fluid and drives the electric generator. This enables a reduction in the size of the control pump with a corresponding increase in the size of the more efficient primary purpers, because the control pump can regulate both positively and negatively on the supply quantity from the primary pumps. If the primary pumps supply more hydraulic fluid than necessary, the regulator pump can consume the excess quantity and produce electrical energy, and if they supply too little, the regulator pump can supply the missing quantity.

In a preferred further development, the control pump has a capacity of from 40 to 60%, preferably mainly 50%, of the capacity of a primary pump and the primary pumps have essentially the same capacity. This 20 distribution of pump sizes minimizes the amount of fluid supplied by the control pump and allows incremental switching on and off of a primary pump virtually without changing the total delivery quantity when the control pump 25 operates at full capacity as a pump or motor.

It is preferred that there are at least four primary pumps and at least two control pumps. This gives suitable small pump sizes combined with very little risk of simultaneous failure of all pumps.

In a preferred embodiment, each primary pump is connected in parallel with an adjustable bypass valve which can return all or part of the hydraulic fluid delivered from the pump to its suction side, and in the primary pump pressure line to the high pressure line there is a check valve located between the high pressure line and 5 DK 173135 B1. the return line with the bypass valve. When no supply quantity is required from the primary pump, the bypass valve can be opened completely with the effect that the pressure in the primary pump pressure line drops almost down to 5 low pressure line pressure, the non-return valve between the high pressure line and the bypass valve blocking the high pressure line pressure from the primary pump and the bypass valve. In this situation, the pressure difference between the suction and pressure side of the primary pump is only caused by the flow resistance 10 in the ring circuit from the low pressure line through the primary pump and return through the return line. The pressure difference is very small and the primary pump consumes only a small amount of energy by being switched off in this way.

In its simplest design, the bypass valve is a shut-off valve with a closed and an open position.

It is also possible to design the bypass valve as a control valve that regulates the supply pressure from the primary pump. This regulation can be common to all 20 primary pumps, so that the pressure in the high-pressure line becomes adjustable in an advantageously simple way where no unnecessary energy has been used to pressurize the hydraulic fluid.

In a preferred embodiment, the pressure in the high pressure line is electronically controlled by means of a valve which adjusts the delivery amount from the control pump. By varying the supply or consumption amount from the control pump, thereby compensating for the differences between the quantity of the primary pumps delivered instantaneously and the instantaneous consumption, the energy loss in the hydraulic system due to failure to utilize the pumps full supply pressure to the "high pressure line can be minimized as the supply pressure is continuous. can be adjusted to correspond to the instantaneous minimum delivery pressure to that of the hydraulic 6 DK 173135 B1 drive devices which require the highest delivery pressure at that operating state.

When the hydraulic system supplies hydraulic pump drives for the fuel pumps and hydraulic actuators for the exhaust valves in an internal combustion engine, the delivery pressure from the high pressure pumps can be at most 75% of the delivery pressure at 100% load of the internal combustion engine when its load is 70% or less.

Thus, a noticeable energy saving is achieved for the drive 10 of the hydraulic high-pressure pumps.

The hydraulic system may advantageously be designed such that a first electronic control unit controls at least one control pump and at least one primary pump bypass valve, and that a second electronic control unit 15 controls at least one other control pump and at least another primary pump bypass valve. The electronic control units primarily control to adjust the instantaneous supply quantity and preferably also the instantaneous delivery pressure from the pumps 20 to the quantity and pressure requirements of the hydraulic consumers. For reasons of reliability, it is preferred that failure to control results in full delivery at maximum pressure. The use of multiple controllers that control both primary and control pumps provides an extremely high safety against complete malfunction of the hydraulic system.

Examples of embodiments of the invention will now be described in more detail with reference to the schematic drawing, which shows a simplified diagram of a hydraulic system for a two-stroke cross-head motor.

A hydraulic system supplies hydraulic fluid under pressure to hydraulic units on a two-stroke cross-head motor. The engine has several cylinders equipped with hydraulic drive devices 1, such as pump drives for 35 fuel pumps and hydraulic actuators for exhaust valves. These two types have different hydraulic fluid consumption at different engine loads, as well as their minimum hydraulic pressure requirements may vary. The hydraulic system must, as a minimum, be able to produce a supply quantity that covers the need for the maximum engine load, where the total consumption is greatest. The maximum engine load will usually also require the greatest delivery pressure.

10 Hydraulic fluid can be delivered from a storage tank and can be, for example, a standard hydraulic oil, but it is preferred that the engine lubricating oil is used as hydraulic fluid and that the system is fed from the engine oil sump 2.

A pre-pump 3 sends the hydraulic fluid through at least one filtration device 4 to a low-pressure line 5, to which four primary pumps 6 and two control pumps 7 are connected. For example, the pre-pump can maintain a pressure in the low-pressure line of between 1 and 5 bar overpressure, typically about 2 bar overpressure, which gives the advantage that the primary pumps are kept filled with hydraulic fluid at a positive suction pressure which counteracts cavitation and dry running in the pumps. Thus, the primary pumps need not be self-priming.

The internal combustion engine can either have a fixed direction of rotation, which for the large two-stroke crossover engines means that the engine is either a stationary drive in a power plant or is a ship engine connected to a propeller with variable pitch, or can be reversible so that the engine can operate at 30 full performance and under approximately the same conditions in both directions of rotation, as is the case for a ship engine connected to a propeller with fixed pitch.

The embodiment 35 illustrated in the drawing provides a reversible two-stroke cross-head motor in a hydraulic fluid tank. The ship's engine has no traditional camshaft, and its exhaust valves and fuel pumps are hydraulically driven and electronically controlled. It is also possible to use a common high-pressure source for 5 constant-pressure fuels, and then omit separate fuel pumps for the individual cylinders, but the hydraulically driven fuel pumps are preferred. Furthermore, the hydraulic drive devices which are provided with hydraulic fluid may also be of other types, such as 10 change-over valves and pumps.

The primary pumps 6 are driven directly by an exchange from one or more shafts of the ship engine, typically the engine crankshaft. The ratio is selected so that the primary pumps get a suitable flow rate when the ship's engine is running at normal full load. For a ship engine with a cylinder bore of 500 mm and a rpm at 100% load of about 125 rpm, the primary pumps can have 11 times higher circulation speed than the driving crankshaft. Larger ship engines can have 20 lower rpm, and the primary pumps can then have even higher gear ratios. The primary pumps can be selected after achieving high efficiency. For example, an axial piston pump may be selected by the German manufacturer Mannesmann-Rexroth GmbH with the main type designation A4FM having an efficiency of approx. η - 0.95.

This is a positive displacement pump with solid depletion, ie. pump capacity depends only on the number of turns on the pump shaft. It is advantageous to choose a fixed displacement pump because it has simple design 30 with resultant high efficiency and high reliability.

Since the ship's engine is reversible, its speed also varies with the engine load, which gives a special advantage in connection with the primary pumps, since the lower rpm at lower load automatically gives a lower delivery rate from the primary pumps while at the same time consuming of hydraulic fluid decreases. However, while the supply quantity from the primary pumps varies proportionally to the ship's engine speed, the consumption changes more than proportionally to the speed. Due to their high efficiency, it will be appropriate to select the total capacity of the primary pumps so that they precisely cover the hydraulic consumption of the engine at 100% engine load.

The primary pumps change direction of rotation at the same time as the shaft, and they are made independent of the direction of rotation by placing each pump in a conduit 8 connected at both ends to both the low and high pressure lines. The lead piece 8 extends between two connections 9 for an inlet line 10 and an outlet line 11. At the connections, the wires may be welded together or otherwise assembled, such as bolted to a T-fitting. The conduits 20 may also be formed as drilled channels in a block-shaped body, and in this case the connections are the places where one channel extends into the other. The supply line 10 may be a single line starting from the low-pressure line 5 and branched to the two connections 9. Alternatively, the connections 9 may each have their own access line to the low-pressure line.

Between the low-pressure line 5 and each of the connections 9 there is a non-return valve 12 and 12 ', which only allows fluid flow in the direction from the low-pressure line to the primary pump. On the discharge side, it is preferred that the two discharge lines be united in a single discharge line prior to connection to a high pressure line 14. One, non-return valve 13 and 13 ', which only allow liquid flow in the direction from the primary pump to the high pressure line, is placed in each of the discharge lines before joining. 10 DK 173135 B1 to the individual cable.

The connection of the primary pumps to the low and high pressure lines in the above manner gives a resultant flow from the low pressure to high pressure lines, regardless of whether the primary pump is operated in one or the other direction of rotation. When the primary pump runs one way around, the hydraulic fluid flows through the supply line branch with the check valve 12 'through the line piece 8 in the left direction of the drawing and 10 is delivered to the high pressure line via the outlet line branch with the check valve 13. As the primary pump runs the opposite way around, the hydraulic fluid flows through the branch branch with the check valve 12 through the line piece 8 in the right direction of the drawing and delivered to the high pressure line via the branch line branch with the check valve 13 '. The primary pumps can supply their full capacity at both directions of rotation, which allows the drive devices to have substantially the same consumption of hydraulic fluid at both directions of rotation. Alternatively, it is possible to insert a reversing gear and a clutch between the drive shaft and each primary pump, but this reduces the benefits of using direct shaft drive of the primary pumps. If the motor is not reversible, the branches of the inlet and outlet lines with associated check valves 12, 12 ', 13 and 13' may be omitted and the lines 10, 11 may be connected directly to the primary pump 6.

At each primary pump there is a return line 15 with a bypass valve 18 in the form of an electronically activated control valve with at least two positions spring-loaded to the outer position shown in the drawing, where the return line is disconnected. When the bypass valve is actuated by a control signal, it switches to the second position where the return line is open. The return line starts from DK 173135 B1 at the outlet line 11 and leads to the low pressure line 5 or another connection point on the suction side of the primary pump. A non-return valve 17 in the discharge line lies between the branch of the return line and the high-pressure line 5 14. The check valve 17 prevents the high pressure in the line 14 from propagating into the area of the return line's branch.

In an alternative embodiment not shown, the bypass valve is designed as an overpressure valve with adjustable opening pressure. When the associated primary pump is desired to be taken out of service / put into operation to adjust the delivered hydraulic flow for instantaneous consumption, the opening pressure can be lowered or lowered below the pressure in the low pressure line, respectively, and raised to an opening pressure 15 greater than the pressure in the high pressure line.

The control pump 7 is an electrically driven, electronically controlled axial piston pump. For example, an axial piston pump can be selected by the German manufacturer Mannesmann-Rexroth GmbH with the main type designation A4VS0, which at 20 full delivery has a maximum efficiency of η - 0.90. At lower delivery volumes, the efficiency is significantly lower. This is a positive displacement pump with variable displacement, in which the pump pistons are pivotally mounted on a disk rotated by the pump shaft and are displaceable in cylinders in a co-rotating drum whose longitudinal axis is angularly adjustable to the longitudinal axis of the pump shaft. By means of a longitudinal slider, the inclination of the drum with the cylinders can be changed to change the stroke length of the pistons. The drum has a neutral position where it coaxially extends the pump shaft so that the pistons have zero stroke. In addition to adjusting the pump delivery amount by adjusting the positive slope of the drum, the slope of the drum '35 can be changed to lie on the other side of the neutral position. Thereby the pump is set to act as a motor rather than as a pump, ie. it can be set to so-called negative supply quantity, where it consumes hydraulic fluid from the high-pressure line and delivers the liquid to the low-pressure line.

The regulator pump is shaft connected to an electric motor / generator unit 19, which drives the regulator pump when it delivers fluid to the high pressure line 14, and is powered by the regulator pump and produces 10 electrical energy when it consumes liquid from the high pressure line. The control pump is adjusted by means of an electronically controlled proportional valve 18 which adjusts the inclination of the drum and thus the operating position of the control pump. The control pump controls the pressure 15 in the high-pressure line via the setting of the valve 18, which can thus be called a pressure control valve. This setting can be done, for example, on the basis of a control voltage, where higher voltage leads to a pressure rise in the high pressure line. The pressure in the high-pressure line 20 for large two-stroke cross-head motors can be suitably controlled to vary within a range of 125 bar to 300 bar, where the low pressures are used at idle loads and the high pressures above 250 bar at 100V load of the motor. By lowering the pressure at lower 25 engine loads, a saving of the energy extracted from the motor system to the pressure setting of the high-pressure liquid in the conduit 14 is achieved.

A control valve 20 is located between the pump 7 and the high-pressure line 14. The control valve has two positions, 30 of which the valve in one places a non-return valve, which only allows flow in the high-pressure line, inside the high-pressure line flow path and in the other position the flow path keeps open. so that the control pump 7 can consume hydraulic fluid from the high pressure line. The control valve 20 is spring-loaded to take the first position, but can be activated electronically to take the second position.

If there is a failure in the electronic control, the control valve 20 forcibly adjusts to the position with active check valve, so that pressure loss from the high pressure line is prevented. The high pressure conduit contains a safety valve which is not shown which can drain fluid if the pressure generated by the primary pumps without pressure control from the control pumps 7 exceeds a predetermined maximum pressure of, for example, 310 bar. If the entire electronic control system fails, all the primary pumps will be forcibly switched on and the control pumps forcibly switched off, resulting in the delivery of full hydraulic power regardless of consumption. Not used hydraulic fluid is discharged via the safety valve in the high pressure line.

As an alternative to the use of the control valve 20 or as an additional safety, the control pump may be provided with an electrically controlled and mechanically acting brake, such as a disc brake with brake pads, which is kept away from the brake disc by a magnetizing current. In the event of a failure of the electrical system, the magnetization current disappears, so mechanical compression springs bring the brake pads to an active braking position in abutment against the brake disc, which slows the regulating pump to a standstill.

The hydraulic system is controlled via two electronic control units 21, each controlling two primary pumps and a control pump, ie. the inlet valves 16, the proportional valve 18 and the control valve 20. In the drawing, the control unit 21 with associated units is surrounded by a dotted line. If only one of the control units 21 fails, the other control unit can still maintain the pressure control in the high pressure line 14.

, 35 The control unit 21 receives measurement signals from a pressure sensor 22 on the low-pressure line 5 and a pressure sensor 23 on the high-pressure line 14 as well as a signal on the instantaneous engine load for use for pressure control 14.

When the internal combustion engine is stopped and is in the ready state, one of the control pumps 7 is started so that the high pressure line 14 is pressurized. If the proportional valve 18 does not receive a control voltage from the control unit 21, the regulating pump 7 may be in a starting position where it pumps a predetermined amount of 10 oil into the high pressure line, for example about 20% of the full supply of the regulating pump. This amount of supply is sufficient to start the internal combustion engine, after which the primary pumps deliver. In reversing, the control pumps can maintain the hydraulic pressure in the lowest speed range.

All the conduits 8, 10 and 11 around the primary purse 6 may be configured as flow passages in a manifold, e.g. drilled channels in a larger, block-shaped body. This reduces the number of pipe joints, 20 fittings and so on. It is also possible to integrate the control pumps 7 into such a manifold. It is possible to design the system with only two primary pumps and a single control pump as well as a single control unit 21, but four or more primary pumps are preferred. For reasons of reliability, it is also preferred that there are at least two control pumps 7, controlled by each control unit.

Claims (10)

DK 173135 B1 A hydraulic system for a combustion engine with multiple fuel pumps and multiple exhaust valves, wherein at least one high pressure pump supplies hydraulic drive devices (1), such as pump drives for the fuel pumps and hydraulic actuators for the exhaust valves, with energy from pressurized hydraulic fluid, comprising: at least three high-pressure pumps, at least two of which are primary pumps (6), 10 which are shaft driven by the internal combustion engine, so that their rpm varies in a predetermined ratio with the rpm of the crankshaft of the engine, and at least one of which is the control pump (7) which is electrically powered and has controllable amount of delivery. Hydraulic system according to claim 1, characterized in that each primary pump (6) provides a constant amount of delivery per shaft rotation. Hydraulic system according to claim 1 or 2, characterized in that the primary pump (6) has a substantially higher efficiency than the control pump (7). Hydraulic system according to one of claims 1-3, characterized in that the control pump (7) is connected to an electric motor / generator unit (19) and is controllable from a pumped state where it is driven by the electric motor and supplies pressurized hydraulic fluid. , for an engine condition where it consumes pressurized hydraulic fluid and drives the electric generator. Hydraulic system according to claim 4, characterized in that the control pump (7) has a capacity of from 40 to 60%, preferably mainly 50%, of the capacity of a primary pump (6) and that the primary pump has substantially the same capacity. Hydraulic system according to one of claims 1 to 5, characterized in that there are at least four primary pumps (6) and at least two control pumps (7). Hydraulic system according to one of claims 1-6, characterized in that each primary pump (6) is connected in parallel with an adjustable bypass valve (16) which can return all or part of the hydraulic fluid delivered from the pump to its suction side. and that in the primary pump (6) pressure line for the high pressure line there is a check valve (17) located between the high pressure line and the return line (15) with the bypass valve. Hydraulic system according to claim 7, characterized in that the pressure in the high-pressure line is electronically controlled by means of a valve (18) which adjusts the delivery amount from the control pump (7). Hydraulic system according to one of claims 1-8, characterized in that the delivery pressure from the high-pressure pumps (6, 7) is at most 75% of the delivery pressure at 100% load of the internal combustion engine when its load is 70% or less. Hydraulic system according to claims 1, 7 and optionally one of claims 2-6, 8 or 9, characterized in that a first electronic control unit (21) controls 20 at least one control pump (7) and at least one primary pump bypass valve (16), and that another electronic control unit controls the memory of one other control pump and at least one other primary pump bypass valve.