US2281626A - Refrigerating apparatus - Google Patents

Description

, Ma.y 5, 1942. H. F. SMITH 4 2,281,626

REFRIGERATING APPARATUS Filed March 31, 1939 INVENTOR.

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ATTORNEYS.

Patented May 5, 1942 REFRIGERATING APPARATUS Harry F. Smith, Lexington, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a

corporation of Delaware Application March 31, 1939, Serial No. 265,284

14 Claims.

This invention relates to refrigeration and more particularly to a refrigeration and generation system for use in railway cars and other installations where it is desirable to both generate electricity and condition air.

One object of this invention is to provide an improved system in which an internal combustion engine such as a Diesel engine or the like is used for driving a generator and a compressor.

A further object of this invention is to provide fully automatic controls for a prime mover whereby the output of the prime mover is at all times equal to the load requirements.

Still another object of this invention is to provide a novel control system for starting and stopping the operation of a dynamo-electric machine.

A further object is to provide a novel control system for controlling the operation of a compressor.

Another object of this invention is to provide an improved arrangement for controlling the speed and output of a Diesel engine.

Another object of this invention is to provide an improved power transmitting system.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred form of the present invention is clearly shown.

In the drawing:

Fig. 1 diagrammatically shows a system embodying features of my invention; and

Fig. 2 diagrammatically shows the circuit arrangement used with the system shown in Fig. 1.

In conditioning air for railway cars, it has been common practice to provide a refrigerating system including a compressor driven-from the live axle of the car. These systems are not entirely satisfactory for various reasons, one of which was that it was difficult to properly compensate for the changes in the speed of the vehicle and the poweravailable.

. In order to overcome the difliculties which were encountered with the old arrangements, I havedevised the system shown in the drawing in which a Diesel engine I is provided for driving the dynamo-electric machine [2 and the compressor I 4. The Diesel engine I0 is provided with a free-wheeling clutch is which may be,

of any conventional and well-known design. The clutch I6 drives the dynamo-electric machine through a belt l8. The dynamo-electric machine shaft carries a first pulley 22 which is driven by the belt l8 and a second pulley 24 which drives the compressor by means of the belt 26. Inasmuch as it is desirable to operate the dynamo-electric machine independently of the compressor, a pneumatic clutch 28 has been provided which makes it possible to operate the dynamo-electric machine as a generator without operating the compressor as will be more fully explained hereinafter. The clutch is controlled by a solenoid valve 30 placed in the air line 32. The compressor 14 is operated whenever refrigeration is required and is in refrigerant flow relationship with the evaporator 34 mounted within the space to be conditioned which, for purposes of illustration, has been'shown as a railway car 36. The refrigerant which is compressed by thlkcompressor l4 discharges into a condenser 38 which is connected to the evaporator by means of the liquid refrigerant line 40 in which is placed an expansion valve 42 or any other conventional control for controlling the flow of refrigerant into the evaporator 34. A fan 44 is provided for circulating air over the evaporator. In order to simplify the illustration no control has been shown for the fan 44. However, the flow of air over the evaporator may be maintained constant or it may be varied in response to changes in the psychrometric condition of the air within the conditioned enclosure in any of several well-known ways. I

The electrical control system for the Diesel engine Hi, the dynamo-electric machine (2 and the compressor l4 comprises a double contact control thermostat generally designated by the reference character 46. The control thermostat 46 includes a first pair of contacts 48 which remain open when full load refrigeration is required and a second pair of contacts 50 which remain closed at all times when the temperature is above a predetermined value at which conditioning is required. The arrangement is such that the contacts close before the contacts 50 open for a purpose to be described more fully hereinafter. I

Referring now to Fig. 2 in which is shown the circuit diagram, the battery-52 is connected across the main lines 54 and 56. For purposes of illustration, the lights 58 represent the load on the electrical system. The usual form of carbon pile voltage regulator 60 has been provided and includes "the solenoid 62 which is responsive to the voltage across the load 58. The solenoid 62 controls the voltage drop across the carbon pile 64 by means of the usual linkage mechanism 66.

The starting switch 68 comprises a first contact 10 which copperates with contact 12 in one extreme position. The contact is connected directly to the main line 58. The startin switch 68 also comprises the solenoid 16 which is placed directlyacross the dynamo-electric machine l2. The circuit shown in Fig. 2 illustrates the position of the various switches prior to the startin of the system and with the temperature sumciently high to require full refrigeration. In order to initiate operation of the system, the starter switch is manually held with contacts 10 and 12 in engagement whereby current flows from the line 56 through the contacts 10 and 12 to the Diesel engine starter.- 80 and to the line 54. The starting switch is held in this position until the engine III has been started at which time a pressure change has been created within the 'engine chambers. This pressure change causes operation of thepressure responsive switch 82 which is placed in series with the signal lamp 84 across the lines '54 and 56. When the signal lamp 84 is lighted, the starter switch 68 is permitted to return to neutral position.

With the thermostat 46 in the position in which it is shown, it is necessary tosupply full capacity refrigeration to the system. I Ordinarily, when a system of this type' is first placed in operation following a .period of idleness, the load on' the compressor driving means is higher than usual for a period of time until the pressures in the refrigeration systemreach normal operating pressures. This latter period is referred to hereinafter as the period of initial pull-down on the refrigeration system. ,The engine I, having been started, will drive the compressor through the freewheeling clutch IS, the generator shaft 20, and the clutch 28. The engine will operate slowly to begin with, but will rather quickly pick up speed until the load capacity of the compressor I4 balances the maximum output of theDiesel engine [0, this maximum output having been adjusted to balance against the maxiacross the battery.

mum refrigeration requirement needed for ini- I tial pull-down of the conditioned space. As the car temperature falls due to the operation of the refrigeration system, the refrigeration requirement will become less, whereby the Diesel engine It) will tend to increase its speed due-to the decreased load on the compressor. The increase in speed of the engine l0 results in an increase in the speed of the dynamo-electricma chine which now functions as a generator. During this initial pull-down on the refrigeration system, the generator has been running as a free member without imposing any appreciable.

load upon the engine. However, as the refrigeration load decreases and the speed of the gen- ,erator increases, the potential across the same increases until the voltage across the generator approaches the battery charging voltage at which time-the solenoid 16 will be sufficiently energized to cause the contact 10 of the starting switch 68 to engage the contact I4. When contact Ill engages contact 14 the generator is connected across the battery in battery charging relationship. Closing of the contacts 10 and I4 placesthe solenoid 16 directly across the battery with the result that the contacts I0 and I4 will be held in engagementgpermanently until they are manually separated. By virtue of this arrangement, the dynamo-electric machine or generator l2 which is also capable of functioning as a motor is automatically brought up to generating or motoring speed, as the conditions require.

' without thenecessity of aspecial motor startin control. This is true since, once the generator.

I! has been placed across the battery 52 by means of the solenoid 18, the generator will act as a generator if its speed is sufllciently high for it 'to generate the required voltage, and it will act as a motor at such times when the speed of the same drops sufiiciently so that the potential across the generator is less than the potential Thus, the generator may either generate or motor without the use of any additional changeover control system.

It will be noted that, with the temperature responsive switch 46 in the position shown in Fig. 2, thegenerator field winding and the resistance 92 are connected in series. By virtue of this series circuit arrangement, the field mit the use of a greater refrigeration capacity at such times when the refrigerating load is high. By providing means for cutting in and out this resistance, it is possible to more closely control the refrigerating 'and generating load conditions. In order to control the speed of the engine l0, a'solenoid coil 94 has been placed directly across the carbon pile 64. This solenoid 94 controls the engine throttle 96. When the resistance 92 is in series with the generator field winding 90, a higher speed of the engine is ob- 'tainable before the solenoid 94 will affect the speed of the engine. Consequently, the compressor is operated at a higher speed during this time when the need for refrigeration is greatest. As the car temperature begins to fall, the con.- tacts 48 will close whereby the resistance 92 is short-circuited. Short-circuiting of the resistance 92 increases the field strength of the generator which, in turn, increases the voltage output of the generator. This increase in generator voltage will influence the voltage regulator '0 which'controls the voltage to the load 58. The change in potential across the voltage regulator causes the solenoid 94 to reduce the speed of the engine "I to a point at which thegeneratcr voltage will be equal to the desired charging voltage. This speed will be somewhat lower than the [former speed and will serve to reduce the refrigeration capacity due to the reduction of the compressor speed. This, however, is desirable since the amount of refrigeration required has been lessened. However, at thisreduced speed, the

properly distribute the power between the refrigcrating load and the generating load. It will also be noted that under both high and low speed conditions the generating load remains substan-- tially constant while the battery is being'charge'd.

Inasmuchas morepower is required to operate tery and at the same time operating the compressor so as to cool the air within the compartment being conditioned and further assuming that the temperature of the compartment has dropped below that normally desired, the-thermostatic switch 46 will operate to open the contacts '0, thereby deenergizing the solenoid H which controls the operation of the valve 30. The deenergization of the solenoid 3| serves to shut oil the air supply to the pneumatic clutch 28 with the result that the compressor I4 is disconnected from the dynamo-electric machine l2, and consequently the Diesel engine It. By disconnecting the compressor from the Diesel engine, the load on the Diesel engine is reduced with the result that the engine will tend to increase its speed and this, in turn, will tend to increase the generator output to the battery above the desired generator charging rate. Inasmuch as an increase in the generator voltage momentarily changes the voltage drop across the coil 94, the throttle 96 of the Diesel engine is operated so as to decrease the speed of the engine I0.

The voltage regulator 60 controls the voltage output from the battery 52 to the car lighting system 58 which, in this case, represents the load; and, as the voltage impressed upon the battery increases, the voltage control 60 causes a change in the carbon pile resister so as to maintain the line voltage at the desired level. The potential across the carbon pile 64, therefore, provides an indication of the voltage being impressed upon the battery by the generator. Consequently, when the voltage from the generator to the battery increases above a desired charging level, the solenoid coil 62 will cause an expansion of the carbon pile 64 with the result that the solenoid 94 will cause a reduction in the speed of the engine III. The engine I will run at suiflcient speed to cause generation as long as the voltage drop across the carbon pile 64 indicates the need for generation. The solenoid 94 operates between a maximum and minimum voltage so that when the battery has become fully charged, the voltage across the carbon pile 64 is at a maximum and the solenoid 94 will have throttled the engine I I so asto maintain the generator voltage equal to under these conditionsfunction as a two-speed control for the dynamo-electric machine l2 which is now operating as a motor.- When the car temperature is high, the contacts 48 will,be open with the result that the resistance 92 is connected 'in series with the field coil 90, thereby reducing the field strength and serving to operate the motor at a higher speed. As the temperature of the car is reduced, the contacts 48 will close so as to short out the resistance 82, By shorting the resistance 92 the field strength is increased whereby the speed of the motor is reduced so as to correspond to the lower refrigeration requirements. In the event that the car temperature is further reduced below that normally desired, the contacts 50 will open'so as to operate the solenoid 3f which then disengages the clutch 28, thereby disconnecting the compressor from the motor.

By virtue of the novel control arrangement described hereinabove, it is possible to balance the power requirements of the compressor and generator againstthe power of the Diesel engine so that after the system has once been started, the system will function completely automatically so as to shift the load from refrigeration to generation to motor drive and back again without a single operation being necessary on the part of the attendant, other than starting the Diesel engine once it has been stopped.

While I have illustrated a system intended to be mounted directly on a railway car for supplying necessary refrigeration on the car and at the same time supplying the necessary amount of electrical energy for operating the necessary electrical devices, it is obvious that the system is equally suitable for a number of other installathe battery voltage, thereby permitting the generator to float upon the battery in the well-known manner. When the engine I0 is operating the generator only and it becomes necessary to start the compressor, the increase in load on the engine, due to the compressors being connected, serves to momentarily cause the engine to slow down. As the engine slows down, the potential across the coil 94 is instrumental in operating the throttle 96 so as to increase the speed of the I engine'until the engine speed is properly balanced with the load.- a

There are times when it is desirable to operate the compressor without operating the engine l0, such as when entering a terminal. Under this condition, the engine can be stopped and the dynamo-electric machine I! will automatically operate as a motor to drive the compressor. Under this condition, the freewheeling clutch it on the engine shaft permits the dynamo-electric machine II to operate as a motor without driving the engine. The thermostatic controls 48 will,

tions where electrical energy and refrigeration are both desired.

While the form of embodiment of theinvem tion as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In combination, an engine, a dynamo-electric machine, torque transmitting means between said engine and said dynamo-electric machine, a battery, load means energized from said battery, a voltage regulator for maintaining the voltage across said load substantially contant, means whereby the speed of said engine is c0ntrolled in response to the voltage drop across said voltage regulator, and means whereby said dynamo-electric machine may be energized as a motor i'rom said battery.

2. In combination, an internal combustion engine, a driven device, torque transmitting means between said engine and said driven device, said torque transmitting means comprising a freewheeling clutch, control means for controlling the speed of said engine so as to balance the power output of said engine with the power requirements of said device, dynamo-electric means for operating said driven device independently of operation of said engine, and temperature responsive means controlling the operation trio machine and said engine, thermostatic control means controlling the operation 01' said enflow connections between means for operating said engine at a first speed during the initial pull-down n the refrigeration system, operating the engine at a second and lower speed subsequent to the initial refrigeration system pull-down, and means for disengaging said compressor from said engine-when no refrigeration is required, said thermostatic control'means comprising means for varying the load imposed on said engine by said dynamoelectric machine.

I 4. A refrigerating system comprising an evaporator; a condenser and a compressor connected in fluid flow relationship, an engine for operating said compressor, a battery, a dynamo-electric machine i circuit with said battery, torque transmitting means between said dynamo-electric machine and said engine, thermostatic control means controlling the operation of said engine, said thermostatic control means comprising means for operating said engine at a first speed during the initial pull-down on the refrigeration system, operating the engine at a second and lower speed subsequent to the initial refrigeration system pull-down, means for disengaging said compressor from said engine when no refrigeration is required, and means for operating said dynamo-electric machine as a motor for driving said compressor when saiii engine is inoperative, said thermostatic control means comprising means for varying the speed of said dynamoelectric 'machine when operating as'a motor for driving said compressor.

5. In combination, an internal combustion engine, a driven device, torque transmitting means between said engine and said driven device, said torque transmitting means comprising a freewheeling clutch, dynamo-electric means for operating said driven device independently of operation of said engine, and automatic control means for controlling the speed of said engine so as to balance the power output of said engine with the power requirements of said device, said control means including means for varying the speed of. said dynamo-electric machine when said dynamo-electric machine vice independently of operation of said engine.

6. The method of controlling the energy out-' put of a dynamo-electric machine which is operated as a motordriving a refrigerant compressor part of thetime and as a generator driven by a separate compressor driving means part of the time which comprises increasing and decreasing the field resistance of said dynamo-electric ma chine so as to vary the -speed of the dynamoelectric machine when operated asa motor and to vary the charging rate when ope ated as a generator driven by said engine.

7. In combination with a power driven vehicle, an auxiliary Diesel engine, a driven device, torque transmitting means between said engine and said driven device, said torque transmitting means comprising a freewheeling clutch, control means for controlling the speed of said engine so as to balance the power output of said engine with the power requirements of said device, dynamo-electric means for operating said driven device independently of operation of said engine, and means whereby said driven member may be operated independently of said engine.

8. In combination, a volatile refrigerant evaporator, a condenser, a compressor, refrigerant said evaporator', eonbattery, a dynamodenser and compressor, a

operates said driven dey I 2,281, gine, said thermostatic control means comprising electric machine for operating said compressor, means for energizing said dynamo-electric machine as a motor from said battery,- temperature responsive means for varying the speed of said -motor, means for operating said dynamo-electric machine as a generator for charging said battery, and means responsive to the output of said generator controlling the speed of said last named means.

9. In combination, a battery, adynamo-elec tric machine comprising a field winding and an armature winding, circuit connections between said battery and said windings, a resistance element in series with one of-said windings, apump operated by said dynamo-electric machine, an-

internal combustion. engine, drive meansbetweensaid engine and said dynamo-electric machine whereby said dynamo-electric machine may be operated as 'a generator driven by said engine, and, means for shunting. said. resistance element in response to a. change in pumping requirements. I

10. In combination, an, engine, a dynamo-electric machine, torque transmitting means including a freewheeling clutch between said engine and said dynamo-electric machine, a refrigerant compressor, torque transmitting means between said compressor and said dynamo-electric machine, said torque transmitting means comprising a clutch for disengaging said compressor from said dynamo-electric machine, control means responsive to refrigerant requirements for varying the speed of said engine, means for energizing said dynamo-electric machine as a motor for operating said compressor independently of said engine, and temperature responsive means controlling the output of said dynamo-electric machine.

11. In combination, an evaporator, a compressor, acondens er, refrigerant flow connections between said evaporator, compressor and condenser, a battery, a generator having a field winding and an armature winding, circuit connections between said generator and said battery, an engine for driving said compressor and said generator, a compressor, a resistance element in series with one of said windings, and thermal means for declutching said compressor at one temperature and for varying said resistance at-a different temperature.

12. In a refrigerating system, an evaporator, means for circulating air to be conditioned in thermal exchange relationship with said evaporator, a condenser and a compressor connected in fluid flow'relationship with said-evaporator, a variable speed engine for operating said compressor, a variable speed motor foroperating said compressor, and control means including,a

thermal element for varying the speed of said engine when said engine operates said compressor and for varying the speed of said motor when said motor operates said compressor.

13. In combination with a power driven vehicle, an auxiliary internal combustion engine,

a refrigerating system including a refrigerant, compressor, torque transmitting means between said en inc and said compressor, said torque transmi ting means comprising a clutzdi, control means for controlling the speed of said engine so as to balance the power. output of said engine with the power requirements of said compressor, dynamo-electric means for operating said compressor independently of operation of said enclutch between'said engine and said gine, and means whereby said compressor may be operated independently of said engine.

14. In combination, a variable speed engine, a variable speed dynamo-electric machine, torque transmitting means between said dynamo-electric machine and said engine, a compressor, torque transmitting means between said compressor and said dynamo-electric machine, a clutch in said first named torque transmitting means, a clutch in said second named torque transmitting means, and means responsive to refrigeration requirements for controlling the speed of said engine.

HARRY F. SMITH.

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